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XML Reading and Writing

 

Fundamentals of Writing to an XML File

 

Introduction

In previous lessons, we learned to process XML files using the Document Object Model as implemented by the XmlDocument class. To go further and make XML friendlier, the .NET Framework provides many other classes for different purposes, allowing you to create and manage nodes from custom .NET classes.

 

 

Practical Learning Practical Learning: Introducing XML-Based Applications

  1. Start Microsoft Visual Studio .NET and create a Windows Forms Application named CollegeParkAutoRepair1
  2. In the Solution Explorer, right-click Form1.vb and click Rename
  3. Type CPAR.vb and press Enter
  4. From the Menus & Toolbars section of the Toolbox, click MenuStrip and click the form
  5. Design the menu items as follows:
     
    MenuItem DropDownItems
    Text Name Text Name Shortcut
    &File mnuFile &New Repair Order mnuFileNew Ctrl+N
        &Open Existing Order... mnuFileOpen Ctrl+O
        &Save Current Order mnuFileSave Ctrl+S
        Separator    
        &Print... mnuFilePrint Ctrl+P
        Print Pre&view... mnuFilePrintPreview  
        Separator    
        E&xit mnuFileExit  
  6. Design the form as follows:
     
    College Park Auto-Repair
    Control Name Text Other Properties
    Group   Order Identification  
    Label   Customer Name:  
    TextBox txtCustomerName    
    Label   Address  
    TextBox txtAddress    
    Label   City:  
    TextBox txtCity    
    Label   State:  
    TextBox txtState    
    Label   ZIP Code:  
    TextBox txtZIPCode   TextAlign: Right
    Label   Make / Model:  
    TextBox txtMake    
    TextBox txtModel    
    Label   Year:  
    TextBox txtCarYear   TextAlign: Right
    Label   Problem Description:  
    TextBox txtProblem    
    GroupBox   Parts Used  
    Label   Part Name  
    Label   Unit Price  
    Label   Qty  
    Label   Sub Total  
    TextBox txtPartName1    
    TextBox txtUnitPrice1 0.00 TextAlign: Right
    TextBox txtQuantity1 0 TextAlign: Right
    TextBox txtSubTotal1 0.00 TextAlign: Right
    Enabled: False
    TextBox txtPartName2    
    TextBox txtUnitPrice2 0.00 TextAlign: Right
    TextBox txtQuantity2 0 TextAlign: Right
    TextBox txtSubTotal2 0.00 TextAlign: Right
    Enabled: False
    TextBox txtPartName3    
    TextBox txtUnitPrice3 0.00 TextAlign: Right
    TextBox txtQuantity3 0 TextAlign: Right
    TextBox txtSubTotal3 0.00 TextAlign: Right
    Enabled: False
    TextBox txtPartName4    
    TextBox txtUnitPrice4 0.00 TextAlign: Right
    TextBox txtQuantity4 0 TextAlign: Right
    TextBox txtSubTotal4 0.00 TextAlign: Right
    Enabled: False
    TextBox txtPartName5    
    TextBox txtUnitPrice5 0.00 TextAlign: Right
    TextBox txtQuantity5 0 TextAlign: Right
    TextBox txtSubTotal5 0.00 TextAlign: Right
    Enabled: False
    GroupBox   Jobs Performed  
    Label   Price  
    TextBox txtJobPerformed1    
    TextBox txtJobPrice1 0.00 TextAlign: Right
    TextBox txtJobPerformed2    
    TextBox txtJobPrice2 0.00 TextAlign: Right
    TextBox txtJobPerformed3    
    TextBox txtJobPrice3 0.00 TextAlign: Right
    TextBox txtJobPerformed4    
    TextBox txtJobPrice4 0.00 TextAlign: Right
    TextBox txtJobPerformed5    
    TextBox txtJobPrice5 0.00 TextAlign: Right
    GroupBox   Order Summary  
    Label   Total Parts:  
    TextBox txtTotalParts 0.00 TextAlign: Right
    Label   Total Labor:  
    TextBox txtTotalLabor 0.00 TextAlign: Right
    Label   Tax Rate:  
    TextBox txtTaxRate 7.75 TextAlign: Right
    Label   %  
    Label   Tax Amount:  
    TextBox txtTaxAmount 0.00 TextAlign: Right
    Label   Total Order:  
    TextBox txtTotalOrder 0.00 TextAlign: Right
    Label   Recommendations  
    TextBox txtRecommendations   Multiline: True
    ScrollBars: Vertical
  7. Right-click the form and click View Code
  8. Just above the Public Class CPAR line, import the following namespaces:
     
    Imports System.IO
    Imports System.Xml
    Imports System.Text
    
    Public Class CPAR
    
    End Class
  9. Under the Public Class CPAR line, create a sub-procedure named Calculate as follows:
      
    Imports System.IO
    Imports System.Xml
    
    Public Class CPAR
        Private Sub Calculate()
            Dim UnitPricePart1 As Double, UnitPricePart2 As Double
            Dim UnitPricePart3 As Double, UnitPricePart4 As Double
            Dim UnitPricePart5 As Double
            Dim SubTotalPart1 As Double, SubTotalPart2 As Double
            Dim SubTotalPart3 As Double, SubTotalPart4 As Double
            Dim SubTotalPart5 As Double, TotalParts As Double
            Dim QuantityPart1 As Integer, QuantityPart2 As Integer
            Dim QuantityPart3 As Integer, QuantityPart4 As Integer
            Dim QuantityPart5 As Integer
            Dim Job1Price As Double, Job2Price As Double
            Dim Job3Price As Double, Job4Price As Double
            Dim Job5Price As Double, TotalLabor As Double
            Dim TaxRate As Double, TaxAmount As Double
            Dim TotalOrder As Double
    
            ' Don't charge a part unless it is clearly identified
            If txtPartName1.Text = "" Then
                txtUnitPrice1.Text = "0.00"
                txtQuantity1.Text = "0"
                txtSubTotal1.Text = "0.00"
                UnitPricePart1 = 0.0
            Else
                Try
                    UnitPricePart1 = CDbl(txtUnitPrice1.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Unit Price")
                    txtUnitPrice1.Text = "0.00"
                    txtUnitPrice1.Focus()
                End Try
    
                Try
                    QuantityPart1 = CInt(txtQuantity1.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Quantity")
                    txtQuantity1.Text = "0"
                    txtQuantity1.Focus()
                End Try
            End If
    
            If txtPartName2.Text = "" Then
                txtUnitPrice2.Text = "0.00"
                txtQuantity2.Text = "0"
                txtSubTotal2.Text = "0.00"
                UnitPricePart2 = 0.0
            Else
                Try
                    UnitPricePart2 = CDbl(txtUnitPrice2.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Unit Price")
                    txtUnitPrice2.Text = "0.00"
                    txtUnitPrice2.Focus()
                End Try
    
                Try
                    QuantityPart2 = CInt(txtQuantity2.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Quantity")
                    txtQuantity2.Text = "0"
                    txtQuantity2.Focus()
                End Try
            End If
    
            If txtPartName3.Text = "" Then
                txtUnitPrice3.Text = "0.00"
                txtQuantity3.Text = "0"
                txtSubTotal3.Text = "0.00"
                UnitPricePart3 = 0.0
            Else
                Try
                    UnitPricePart3 = CDbl(txtUnitPrice3.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Unit Price")
                    txtUnitPrice3.Text = "0.00"
                    txtUnitPrice3.Focus()
                End Try
    
                Try
                    QuantityPart3 = CInt(txtQuantity3.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Quantity")
                    txtQuantity3.Text = "0"
                    txtQuantity3.Focus()
                End Try
            End If
    
            If txtPartName4.Text = "" Then
                txtUnitPrice4.Text = "0.00"
                txtQuantity4.Text = "0"
                txtSubTotal4.Text = "0.00"
                UnitPricePart4 = 0.0
            Else
                Try
                    UnitPricePart4 = CDbl(txtUnitPrice4.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Unit Price")
                    txtUnitPrice4.Text = "0.00"
                    txtUnitPrice4.Focus()
                End Try
    
                Try
                    QuantityPart4 = CInt(txtQuantity4.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Quantity")
                    txtQuantity4.Text = "0"
                    txtQuantity4.Focus()
                End Try
            End If
    
            If txtPartName5.Text = "" Then
                txtUnitPrice5.Text = "0.00"
                txtQuantity5.Text = "0"
                txtSubTotal5.Text = "0.00"
                UnitPricePart5 = 0.0
            Else
                Try
                    UnitPricePart5 = CDbl(txtUnitPrice5.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Unit Price")
                    txtUnitPrice5.Text = "0.00"
                    txtUnitPrice5.Focus()
                End Try
    
                Try
                    QuantityPart5 = CInt(txtQuantity5.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Quantity")
                    txtQuantity5.Text = "0"
                    txtQuantity5.Focus()
                End Try
            End If
    
            ' Don't bill the customer for a job that is not specified
            If txtJobDescription1.Text = "" Then
                txtJobPrice1.Text = "0.00"
                Job1Price = 0.0
            Else
                Try
                    job1Price = CDbl(txtJobPrice1.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Job Price")
                    txtJobPrice1.Text = "0.00"
                    txtJobPrice1.Focus()
                End Try
            End If
    
            If txtJobDescription2.Text = "" Then
                txtJobPrice2.Text = "0.00"
                job2Price = 0.0
            Else
                Try
                    job2Price = CDbl(txtJobPrice2.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Job Price")
                    txtJobPrice2.Text = "0.00"
                    txtJobPrice2.Focus()
                End Try
            End If
    
            If txtJobDescription3.Text = "" Then
                txtJobPrice3.Text = "0.00"
                job3Price = 0.0
            Else
                Try
                    job3Price = CDbl(txtJobPrice3.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Job Price")
                    txtJobPrice3.Text = "0.00"
                    txtJobPrice3.Focus()
                End Try
            End If
    
            If txtJobDescription4.Text = "" Then
                txtJobPrice4.Text = "0.00"
                job4Price = 0.0
            Else
                Try
                    job4Price = CDbl(txtJobPrice4.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Job Price")
                    txtJobPrice4.Text = "0.00"
                    txtJobPrice4.Focus()
                End Try
            End If
    
            If txtJobDescription5.Text = "" Then
                txtJobPrice5.Text = "0.00"
                job5Price = 0.0
            Else
                Try
                    job5Price = CDbl(txtJobPrice5.Text)
                Catch Exc As FormatException
                    MsgBox("Invalid Job Price")
                    txtJobPrice5.Text = "0.00"
                    txtJobPrice5.Focus()
                End Try
            End If
    
            SubTotalPart1 = UnitPricePart1 * QuantityPart1
            SubTotalPart2 = UnitPricePart2 * QuantityPart2
            SubTotalPart3 = UnitPricePart3 * QuantityPart3
            SubTotalPart4 = UnitPricePart4 * QuantityPart4
            SubTotalPart5 = UnitPricePart5 * QuantityPart5
    
            txtSubTotal1.Text = FormatNumber(SubTotalPart1)
            txtSubTotal2.Text = FormatNumber(SubTotalPart2)
            txtSubTotal3.Text = FormatNumber(SubTotalPart3)
            txtSubTotal4.Text = FormatNumber(SubTotalPart4)
            txtSubTotal5.Text = FormatNumber(SubTotalPart5)
    
            TotalParts = SubTotalPart1 + SubTotalPart2 + _
                         SubTotalPart3 + SubTotalPart4 + SubTotalPart5
    
            TotalLabor = Job1Price + Job2Price + Job3Price + _
                            Job4Price + Job5Price
    
            Try
                TaxRate = CDbl(txtTaxRate.Text)
            Catch Exc As FormatException
                MsgBox("Invalid Tax Rate")
                txtTaxRate.Text = "7.75"
                txtTaxRate.Focus()
            End Try
    
            Dim totalPartsAndLabor As Double = totalParts + totalLabor
            TaxAmount = totalPartsAndLabor * TaxRate / 100
            TotalOrder = totalPartsAndLabor + TaxAmount
    
            txtTotalParts.Text = FormatNumber(TotalParts)
            txtTotalLabor.Text = FormatNumber(TotalLabor)
            txtTaxAmount.Text = FormatNumber(TaxAmount)
            txtTotalOrder.Text = FormatNumber(TotalOrder)
        End Sub
    End Class
  10. In the Class Name combo box, select mnuFileNew
  11. In the Method Name combo box, select Click and implement the event as follows:
     
    Private Sub mnuFileNew_Click(ByVal sender As Object, _
                                     ByVal e As System.EventArgs) _
                                     Handles mnuFileNew.Click
            txtCustomerName.Text = ""
            txtAddress.Text = ""
            txtCity.Text = ""
            txtState.Text = ""
            txtZIPCode.Text = ""
            txtMake.Text = ""
            txtModel.Text = ""
            txtCarYear.Text = ""
            txtProblem.Text = ""
    
            txtPartName1.Text = ""
            txtUnitPrice1.Text = "0.00"
            txtQuantity1.Text = "0"
            txtSubTotal1.Text = "0.00"
            txtPartName2.Text = ""
            txtUnitPrice2.Text = "0.00"
            txtQuantity2.Text = "0"
            txtSubTotal2.Text = "0.00"
            txtPartName3.Text = ""
            txtUnitPrice3.Text = "0.00"
            txtQuantity3.Text = "0"
            txtSubTotal3.Text = "0.00"
            txtPartName4.Text = ""
            txtUnitPrice4.Text = "0.00"
            txtQuantity4.Text = "0"
            txtSubTotal4.Text = "0.00"
            txtPartName5.Text = ""
            txtUnitPrice5.Text = "0.00"
            txtQuantity5.Text = "0"
            txtSubTotal5.Text = "0.00"
    
            txtJobDescription1.Text = ""
            txtJobPrice1.Text = "0.00"
            txtJobDescription2.Text = ""
            txtJobPrice2.Text = "0.00"
            txtJobDescription3.Text = ""
            txtJobPrice3.Text = "0.00"
            txtJobDescription4.Text = ""
            txtJobPrice4.Text = "0.00"
            txtJobDescription5.Text = ""
            txtJobPrice5.Text = "0.00"
    
            txtTotalParts.Text = "0.00"
            txtTotalLabor.Text = "0.00"
            txtTaxRate.Text = "7.75"
            txtTaxAmount.Text = "0.00"
            txtTotalOrder.Text = "0.00"
    
            txtRecommendations.Text = ""
            txtCustomerName.Focus()
    End Sub
  12. Under the above End Sub line, create the following common eventand click the first text box under Unit Price
  13. In the Properties window, click the Events button and double-click Leave
  14. Call the Calculate() method as follows:
     
    Private Sub ControlsLeave(ByVal sender As Object, _
                                  ByVal e As EventArgs) _
                                  Handles txtUnitPrice1.Leave, _
                                          txtUnitPrice2.Leave, _
                                          txtUnitPrice3.Leave, _
                                          txtUnitPrice4.Leave, _
                                          txtUnitPrice5.Leave, _
                                          txtQuantity1.Leave, _
                                          txtQuantity2.Leave, _
                                          txtQuantity3.Leave, _
                                          txtQuantity4.Leave, _
                                          txtQuantity5.Leave, _
                                          txtJobPrice1.Leave, _
                                          txtJobPrice2.Leave, _
                                          txtJobPrice3.Leave, _
                                          txtJobPrice4.Leave, _
                                          txtJobPrice5.Leave, _
                                          txtTaxRate.Leave
            Calculate()
    End Sub
  15. Return to the form
  16. From the Printing section of the Toolbox, click the PrintDocument button PrintDocument and click the form
  17. While the print document control is still selected, in the Properties window, change its name to docPrint
  18. Right-click the form and click View Code
  19. In the Class name combo box, select docPrint
  20. In the Method Name combo box, select PrintPage and implement the event as follows:
     
    Private Sub docPrint_PrintPage(ByVal sender As Object, _
                   ByVal e As System.Drawing.Printing.PrintPageEventArgs) _
                                       Handles docPrint.PrintPage
        e.Graphics.DrawLine(New Pen(Color.Black, 2), 60, 90, 680, 90)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), 60, 93, 680, 93)
    
        Dim strDisplay As String = "College Park Auto Repair"
        Dim fntString As System.Drawing.Font = _
    		New Font("Times New Roman", 28, _
        		         FontStyle.Bold)
        e.Graphics.DrawString(strDisplay, fntString, _
                        Brushes.Black, 160, 100)
    
        strDisplay = "Customer Car Repair Order"
        fntString = New System.Drawing.Font("Times New Roman", 18, _
                        FontStyle.Bold)
        e.Graphics.DrawString(strDisplay, fntString, _
                    Brushes.Black, 220, 150)
    
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
        			60, 184, 680, 184)
        e.Graphics.DrawLine(New Pen(Color.Black, 2), _
    			60, 187, 680, 187)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    					12, FontStyle.Bold)
        e.Graphics.DrawString("Order Identification", fntString, _
        		          Brushes.Black, 80, 200)
    
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 250, 640, 250)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    					10, FontStyle.Bold)
        e.Graphics.DrawString("Customer Name:", fntString, _
        			  Brushes.Black, 100, 260)
        fntString = New System.Drawing.Font("Times New Roman", 10, _
        			                FontStyle.Regular)
        e.Graphics.DrawString(txtCustomerName.Text, fntString, _
        	                  Brushes.Black, 260, 260)
    
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 280, 640, 280)
    
        fntString = New Font("Times New Roman", 10, FontStyle.Bold)
        e.Graphics.DrawString("Address:", fntString, _
    		            Brushes.Black, 100, 290)
        fntString = New Font("Times New Roman", _
     			 10, FontStyle.Regular)
        e.Graphics.DrawString(txtAddress.Text, fntString, _
        		          Brushes.Black, 260, 290)
    
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 310, 640, 310)
    
        fntString = New Font("Times New Roman", _
    			 10, FontStyle.Regular)
        Dim strAddress As String = txtCity.Text.ToString()& ", " & _
        			    txtState.Text(+" " & txtZIPCode.Text)
        e.Graphics.DrawString(strAddress, fntString, _
     			  Brushes.Black, 260, 320)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 340, 640, 340)
    
        fntString = New Font("Times New Roman", 10, FontStyle.Bold)
        e.Graphics.DrawString("Car:", fntString, _
    			  Brushes.Black, 100, 350)
        fntString = New Font("Times New Roman", _
    			 10, FontStyle.Regular)
        Dim strCar As String = txtMake.Text & ", " & txtModel.Text & _
                                ", " & txtCarYear.Text
        e.Graphics.DrawString(strCar, fntString, _
      			  Brushes.Black, 260, 350)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 370, 640, 370)
    
        fntString = New Font("Times New Roman", 10, FontStyle.Bold)
        e.Graphics.DrawString("Problem Description:", fntString, _
                    Brushes.Black, 100, 380)
        fntString = New Font("Times New Roman", _
    			 10, FontStyle.Regular)
        e.Graphics.DrawString(txtProblem.Text, fntString, _
                                  Brushes.Black, _
                                  New RectangleF(260, 380, 420, 380))
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 400, 640, 400)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    					12, FontStyle.Bold)
        e.Graphics.DrawString("Parts Used", fntString, _
        		            Brushes.Black, 80, 430)
    
        e.Graphics.DrawLine(New Pen(Color.Black, 2), _
    			80, 450, 680, 450)
    
        e.Graphics.DrawString("Parts Name", fntString, _
    		            Brushes.Black, 100, 460)
        e.Graphics.DrawString("Unit Price", fntString, _
        		          Brushes.Black, 420, 460)
        e.Graphics.DrawString("Qty", fntString, _
        		          Brushes.Black, 520, 460)
        e.Graphics.DrawString("Sub-Total", fntString, _
        		          Brushes.Black, 562, 460)
    
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 480, 640, 480)
    
        fntString = New Font("Times New Roman", 10, _
    			 FontStyle.Regular)
        Dim fmtString As StringFormat = New StringFormat
        fmtString.Alignment = StringAlignment.Far
    
        e.Graphics.DrawString(txtPartName1.Text, fntString, _
        		          Brushes.Black, 100, 490)
        e.Graphics.DrawString(txtUnitPrice1.Text, fntString, _
        		        Brushes.Black, 480, 490, fmtString)
        e.Graphics.DrawString(txtQuantity1.Text, fntString, _
        		        Brushes.Black, 540, 490, fmtString)
        e.Graphics.DrawString(txtSubTotal1.Text, fntString, _
        		        Brushes.Black, 630, 490, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
        		            100, 510, 640, 510)
    
        e.Graphics.DrawString(txtPartName2.Text, fntString, _
                Brushes.Black, 100, 520)
        e.Graphics.DrawString(txtUnitPrice2.Text, fntString, _
                Brushes.Black, 480, 520, fmtString)
        e.Graphics.DrawString(txtQuantity2.Text, fntString, _
                Brushes.Black, 540, 520, fmtString)
        e.Graphics.DrawString(txtSubTotal2.Text, fntString, _
                Brushes.Black, 630, 520, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 540, 640, 540)
    
        e.Graphics.DrawString(txtPartName3.Text, fntString, _
                Brushes.Black, 100, 550)
        e.Graphics.DrawString(txtUnitPrice3.Text, fntString, _
                Brushes.Black, 480, 550, fmtString)
        e.Graphics.DrawString(txtQuantity3.Text, fntString, _
                Brushes.Black, 540, 550, fmtString)
        e.Graphics.DrawString(txtSubTotal3.Text, fntString, _
                Brushes.Black, 630, 550, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
                    100, 570, 640, 570)
    
        e.Graphics.DrawString(txtPartName4.Text, fntString, _
                Brushes.Black, 100, 580)
        e.Graphics.DrawString(txtUnitPrice4.Text, fntString, _
                Brushes.Black, 480, 580, fmtString)
        e.Graphics.DrawString(txtQuantity4.Text, fntString, _
                Brushes.Black, 540, 580, fmtString)
        e.Graphics.DrawString(txtSubTotal4.Text, fntString, _
                Brushes.Black, 630, 580, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 600, 640, 600)
    
        e.Graphics.DrawString(txtPartName5.Text, fntString, _
                Brushes.Black, 100, 610)
        e.Graphics.DrawString(txtUnitPrice5.Text, fntString, _
                Brushes.Black, 480, 610, fmtString)
        e.Graphics.DrawString(txtQuantity5.Text, fntString, _
                Brushes.Black, 540, 610, fmtString)
        e.Graphics.DrawString(txtSubTotal5.Text, fntString, _
                Brushes.Black, 630, 610, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 630, 640, 630)
    
        fntString = New Font("Times New Roman", _
    			12, FontStyle.Bold)
        e.Graphics.DrawString("Jobs Performed", fntString, _
                Brushes.Black, 80, 650)
        e.Graphics.DrawLine(New Pen(Color.Black, 2), _
    			80, 670, 680, 670)
    
        e.Graphics.DrawString("Job Name", fntString, _
    			Brushes.Black, 100, 680)
        e.Graphics.DrawString("Price", fntString, _
    			Brushes.Black, 562, 680)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 700, 640, 700)
    
        fntString = New Font("Times New Roman", 10, _
    			FontStyle.Regular)
    
        e.Graphics.DrawString(txtJobDescription1.Text, fntString, _
                Brushes.Black, 100, 710)
        e.Graphics.DrawString(txtJobPrice1.Text, fntString, _
                Brushes.Black, 600, 710, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 730, 640, 730)
    
        e.Graphics.DrawString(txtJobDescription2.Text, fntString, _
                Brushes.Black, 100, 740)
        e.Graphics.DrawString(txtJobPrice2.Text, fntString, _
                Brushes.Black, 600, 740, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 760, 640, 760)
    
        e.Graphics.DrawString(txtJobDescription3.Text, fntString, _
                Brushes.Black, 100, 770)
        e.Graphics.DrawString(txtJobPrice3.Text, fntString, _
                    Brushes.Black, 600, 770, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 790, 640, 790)
    
        e.Graphics.DrawString(txtJobDescription4.Text, _
    			fntString, Brushes.Black, 100, 800)
        e.Graphics.DrawString(txtJobPrice4.Text, fntString, _
                    Brushes.Black, 600, 800, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 820, 640, 820)
    
        e.Graphics.DrawString(txtJobDescription5.Text, _
    			fntString, Brushes.Black, 100, 830)
        e.Graphics.DrawString(txtJobPrice5.Text, fntString, _
                    Brushes.Black, 600, 830, fmtString)
        e.Graphics.DrawLine(New Pen(Color.Black, 1), _
    			100, 850, 640, 850)
    
        fntString = New System.Drawing.Font("Times New Roman", _
      			12, FontStyle.Bold)
        e.Graphics.DrawString("Order Summary", fntString, _
                    Brushes.Black, 80, 870)
        e.Graphics.DrawLine(New Pen(Color.Black, 2), _
    			80, 890, 680, 890)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Bold)
        e.Graphics.DrawString("Total Parts:", fntString, _
                    Brushes.Black, 500, 900)
        fntString = New System.Drawing.Font("Times New Roman", _
     			10, FontStyle.Regular)
        e.Graphics.DrawString(txtTotalParts.Text, fntString, _
                    Brushes.Black, 640, 900, fmtString)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Bold)
        e.Graphics.DrawString("Total Labor:", fntString, _
                    Brushes.Black, 500, 920)
        fntString = New System.Drawing.Font("Times New Roman", _
     			10, FontStyle.Regular)
        e.Graphics.DrawString(txtTotalLabor.Text, fntString, _
                    Brushes.Black, 640, 920, fmtString)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Bold)
        e.Graphics.DrawString("Tax Rate:", fntString, _
                    Brushes.Black, 500, 940)
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Regular)
        e.Graphics.DrawString(txtTaxRate.Text, fntString, _
                    Brushes.Black, 640, 940, fmtString)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Bold)
        e.Graphics.DrawString("Tax Amount:", fntString, _
                    Brushes.Black, 500, 960)
        fntString = New System.Drawing.Font("Times New Roman", _
     			10, FontStyle.Regular)
        e.Graphics.DrawString(txtTaxAmount.Text, fntString, _
                    Brushes.Black, 640, 960, fmtString)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Bold)
        e.Graphics.DrawString("Repair Total:", fntString, _
                    Brushes.Black, 500, 980)
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Regular)
        e.Graphics.DrawString(txtTotalOrder.Text, fntString, _
                    Brushes.Black, 640, 980, fmtString)
    
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Bold)
        e.Graphics.DrawString("Recommendations:", fntString, _
                Brushes.Black, 100, 900)
        fntString = New System.Drawing.Font("Times New Roman", _
    			10, FontStyle.Regular)
        e.Graphics.DrawString(txtRecommendations.Text, fntString, _
                    Brushes.Black, New RectangleF(100, 920, 350, 280))
    End Sub
  21. Return to the form
  22. From the Printing section of the Toolbox, click the PrintDialog button PrintDialog and click the form
  23. While the print control is still selected, in the Properties window, change its Name to dlgPrint 
  24. Click Document and select docPrint
  25. Right-click the form and click View Code
  26. In the Class Name combo box, select mnuFilePrint
  27. In the Method Name combo box, select Click and implement the event as follows:
     
    Private Sub mnuFilePrint_Click(ByVal sender As Object, _
                                       ByVal e As System.EventArgs) _
                                       Handles mnuFilePrint.Click
            If dlgPrint.ShowDialog() = DialogResult.OK Then
                docPrint.Print()
            End If
    End Sub
  28. Return to the form
  29. From the Printing section of the Toolbox, click PrintPreviewDialog and click the form
  30. In the Properties window, change its (Name) to dlgPrintPreview
  31. Still in the Properties windows, set its Document property to docPrint
  32. Right-click the form and click View Code
  33. In the Class Name combo box, select mnuFilePrintPreview
  34. In the Method Name combo box, select Click and implement the event as follows:
     
    Private Sub mnuFilePrintPreview_Click(ByVal sender As Object, _
                                              ByVal e As System.EventArgs) _
                                              Handles mnuFilePrintPreview.Click
            dlgPrintPreview.ShowDialog()
    End Sub
  35. Save the file
  36. Return to the form

The XML Text Writer Fundamentals

Besides the XmlDocument and the derived classes of XmlNode, the .NET Framework provides the XmlTextWriter class, which is derived from XmlWriter. The XmlTextWriter class works in a top-down approach to create, or deal with, the contents of an XML file. This class writes an XML node and moves down without referring back:

This means that, once you have created a node using the XmlTextWriter, you have no way of referring back to it.

To use an XmlTextWriter object, first declare a variable of the type of this class and initialize it using one of its three constructors.

If you had already created a Stream-based object such as declaring a variable of type FileStream but you did not define an encoding scheme, you can pass the Stream-based object to an XmlTextWriter but you must take this time to specify the encoding scheme. To support this concept, the XmlTextWriter provides a constructor with the following syntax:

Public Sub New(w As Stream, encoding As Encoding)

The first argument of this constructor can be a Stream-based variable. The second argument specifies the encoding scheme that would be applied. The default is UTF-8. Based on this, if you want to use the UTF-8 encoding scheme, you can pass it or pass the argument as 0. If you want to use another encoding scheme, pass it to the constructor.

To work from scratch, that is, to initiate a file with manually-created nodes, you can pass the desired name of the file to the XmlTextWriter constructor using the following syntax:

Public Sub New(filename As String, encoding As Encoding)

In this case, you must provide the name of, or path to, the file, whose content you are creating, as the first argument. You must pass the desired encoding scheme as the second argument. Here is an example:

Imports System.Xml
Imports System.IO
Imports System.Text

Public Class Exercise

    Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)
    End Sub
End Class

Eventually, when you have finished using the XmlTextWriter object, you must free the memory it was using by calling the XmlTextWriter.Flush() method. To release the resources that the object was using, call the XmlTextWriter.Close() method. Here is an example:

Imports System.Xml
Imports System.IO
Imports System.Text

Public Class Exercise

    Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.Flush()
        Writer.Close()
    End Sub
End Class

Creating the XML Declaration

Declaring an XmlTextWriter variable allows you to indicate that you intend to create a new XML file. With the variable ready, you can start writing the file's content. As mentioned in previous lessons, an XML file starts at the top with an XML declaration. To create this declaration, you can call the XmlTextWriter.WriteStartDocument() method. This method is overloaded with two versions. The syntax of one of them is:

Public Overrides Sub WriteStartDocument

This method creates a declaration, sets the XML version to 1.0, and includes the encoding scheme you specified in the constructor. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.Flush()
        Writer.Close()
End Sub

To end an XML file, you must close its declaration. This is done by calling the XmlTextWriter.WriteEndDocument() method. Its syntax is:

Public Overrides Sub WriteEndDocument

This method indicates that the XML file has ended and allows the compiler to stop reading it down. This would be done as follows:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

Creating the Root Element

Between the XML declaration and the end of the file, that is, between the call to XmlTextWriter.WriteStartDocument() and the call to XmlTextWriter.WriteEndDocument() methods, you can create the necessary nodes of the file. As reviewed in previous lessons, the most regular node of an XML file is the element. To create an element, the XmlTextWriter class provides the WriteStartElement() method that is overloaded with various versions. One of the versions of this method, and that is inherited from the XmlWriter class, uses the following syntax:

Public Sub WriteStartElement(localName As String)

This method takes as argument the name of the element that will be created. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

As you may know from XML, every element must be closed. To close an XML element, call the XmlTextWriter.WriteEndElement() method. Its syntax is:

Public Overrides Sub WriteEndElement

When calling this method, always make sure that you know the element it is closing, which must correspond to an appropriate previous call to a WriteStartElement() method. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")
        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

This would produce:

XML Preview

As you can see from the result, a single or the first call to the WriteStartElement() method creates the root element that is required for every XML file. This means that, after this (first) call but before its corresponding WriteEndElement() call, you can create the necessary nodes that you want to include as part of the file.

Creating the Child Elements of the Root

To help you create child elements of the root node, you can keep calling the XmlTextWriter.WriteStartElement() method as necessary and appropriately closing it. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
    Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

    Writer.WriteStartDocument()

    Writer.WriteStartElement("students")

        Writer.WriteStartElement("student")
        Writer.WriteEndElement()

        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

If you simply call this method as done above, the element would be empty. Based on this, the above code would produce:

XML Preview

If you want the element to have a value, call the XmlTextWriter.WriteString() method. Its syntax is:

Public Overrides Sub WriteString(text As String)

This method must immediately follow the call to WriteStartElement() that creates a new element. It takes as argument the value for the immediately previously defined element. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")

        Writer.WriteStartElement("student")
        Writer.WriteString("Raymond Sanson")
        Writer.WriteEndElement()

        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

 This would produce:

XML Preview

If you call the XmlTextWriter.WriteStartElement() method and you want the element to have a value, remember to call the XmlTextWriter.WriteString() method, and then call the XmlTextWriter.WriteEndElement() method. An alternative is to call the XmlWriter.WriteElementString() method that comes in two versions. The syntax of one of these versions is:

Public Sub WriteElementString(localName As String, _
			      value As String)

The first argument to this method is the name of the element that will be created. The second argument is the value of the element. This method creates and closes its element. Here is an example:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = _
            New XmlTextWriter("students.xml", Encoding.UTF8)

        Writer.WriteStartDocument()

        Writer.WriteStartElement("students")

        Writer.WriteStartElement("student")
        Writer.WriteString("Raymond Sanson")
        Writer.WriteEndElement()

        Writer.WriteElementString("student", "Brigitte Arano")

        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

This would produce:

XML Preview

In the same way, you can create the necessary elements and their child elements as necessary. Be careful to appropriately start an element and remember to close it if necessary. Here are examples:

Private Sub btnDocument_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles btnDocument.Click
        Dim Writer As XmlTextWriter = New XmlTextWriter("students.xml", _
                                                    Encoding.UTF8)

        Writer.WriteStartDocument()

        ' Create the root element named students
        Writer.WriteStartElement("students")

        ' Start a child element named student
        Writer.WriteStartElement("student")

        ' Create a number for the student
        Writer.WriteStartElement("studentnumber")
        Writer.WriteString("740597")
        Writer.WriteEndElement()

        ' Create a name for the student
        Writer.WriteStartElement("fullname")
        Writer.WriteString("Christie Aronson")
        Writer.WriteEndElement()

        ' Create a date of birth for the student
        Writer.WriteStartElement("dateofbirth")
        Writer.WriteString("02/16/1988")
        Writer.WriteEndElement()

        ' Create a Format child element to the Video element
        Writer.WriteStartElement("Gender")
        Writer.WriteString("Female")
        Writer.WriteEndElement()

        ' Close the student node
        Writer.WriteEndElement()

        ' Start a new student element
        Writer.WriteStartElement("student")

        ' Create the child elements of the new student element
        Writer.WriteElementString("studentnumber", "249575")
        Writer.WriteElementString("fullname", "Julius Raymonds")
        Writer.WriteElementString("dateofbirth", "12/07/1992")
        Writer.WriteElementString("Gender", "Male")
        ' The current student node
        Writer.WriteEndElement()

        ' Close the root element
        Writer.WriteEndElement()

        Writer.WriteEndDocument()

        Writer.Flush()
        Writer.Close()
End Sub

This would produce:

XML Preview

 

Practical LearningPractical Learning: Creating the Elements of an XML File

  1. From the Dialogs section of the Toolbox, click SaveFileDialog and click the form
  2. Change its properties as follows:
    Title: Save Current Repair Order
    DefaultExt: xml
    Filter: Repair Orders (*.xml)|*.xml|All Files|
    Name: dlgSave
  3. Right-click the form and click View Code
  4. In the Class Name combo box, select mnuFileSave
  5. In the Method Name combo box, select Click and implement the event as follows:
     
    Private Sub mnuFileSave_Click(ByVal sender As Object, _
                                  ByVal e As System.EventArgs) _
                                  Handles mnuFileSave.Click
        ' Just in case, calculate the order now
        Calculate()
        ' This number will be used to incrementally
        ' create the files by their names
        Dim iFilename As Integer
        Dim Filename As String
        ' If this directory doesn't exist, create it
        ' Also, get a reference to this directory for later use
        Dim FolderName As String = "C:\College Park Auto Repair"
        Dim Folder As DirectoryInfo = Directory.CreateDirectory(FolderName)
    
        ' Get the list of files, if any, from the above folder
        Dim ListOfFiles() As FileInfo = Folder.GetFiles("*.xml")
    
        ' If there is no XML file in the directory,
        ' then get ready to create the first file
        If ListOfFiles.Length = 0 Then
            ' Create the name of the (initial) file
            iFilename = 1000
        Else ' If there was at least one file in the directory
            ' Get a reference to the last file
            Dim fleLast As FileInfo = ListOfFiles(ListOfFiles.Length - 1)
            ' Get the name of the last file without its extension
            Dim fwe As String = Path.GetFileNameWithoutExtension(fleLast.FullName)
            ' Get the name of the file
            iFilename = CInt(fwe)
        End If
    
        Filename = FolderName& """" & cstr(iFilename + 1)& ".xml"
    
        ' Get ready to display it in the Save dialog box
        dlgSave.FileName = Filename
    
        ' Find out if the user clicked OK after displaying the Save dialog box
        If dlgSave.ShowDialog() = DialogResult.OK Then
            Dim wtrRepairOrder As XmlTextWriter = New XmlTextWriter(Filename, _
                        Encoding.UTF8)
    
            ' Create the contents of the XML file
            ' Notice that we are not making an attempt to check the values
            wtrRepairOrder.WriteStartDocument()
    
            wtrRepairOrder.WriteStartElement("RepairOrders")
            wtrRepairOrder.WriteStartElement("Invoice")
    
            wtrRepairOrder.WriteElementString("CustomerName", txtCustomerName.Text)
                wtrRepairOrder.WriteElementString("Addres", txtAddress.Text)
                wtrRepairOrder.WriteElementString("City", txtCity.Text)
                wtrRepairOrder.WriteElementString("State", txtState.Text)
                wtrRepairOrder.WriteElementString("ZIPCode", txtZIPCode.Text)
                wtrRepairOrder.WriteElementString("Make", txtMake.Text)
                wtrRepairOrder.WriteElementString("Model", txtModel.Text)
                wtrRepairOrder.WriteElementString("CarYear", txtCarYear.Text)
            wtrRepairOrder.WriteElementString("ProbDescription", txtProblem.Text)
                wtrRepairOrder.WriteElementString("PartName1", txtPartName1.Text)
                wtrRepairOrder.WriteElementString("UnitPrice1", txtUnitPrice1.Text)
                wtrRepairOrder.WriteElementString("Quantity1", txtQuantity1.Text)
                wtrRepairOrder.WriteElementString("SubTotal1", txtSubTotal1.Text)
                wtrRepairOrder.WriteElementString("PartName2", txtPartName2.Text)
                wtrRepairOrder.WriteElementString("UnitPrice2", txtUnitPrice2.Text)
                wtrRepairOrder.WriteElementString("Quantity2", txtQuantity2.Text)
                wtrRepairOrder.WriteElementString("SubTotal2", txtSubTotal2.Text)
                wtrRepairOrder.WriteElementString("PartName3", txtPartName3.Text)
                wtrRepairOrder.WriteElementString("UnitPrice3", txtUnitPrice3.Text)
                wtrRepairOrder.WriteElementString("Quantity3", txtQuantity3.Text)
                wtrRepairOrder.WriteElementString("SubTotal3", txtSubTotal3.Text)
                wtrRepairOrder.WriteElementString("PartName4", txtPartName4.Text)
                wtrRepairOrder.WriteElementString("UnitPrice4", txtUnitPrice4.Text)
                wtrRepairOrder.WriteElementString("Quantity4", txtQuantity4.Text)
                wtrRepairOrder.WriteElementString("SubTotal4", txtSubTotal4.Text)
                wtrRepairOrder.WriteElementString("PartName5", txtPartName5.Text)
                wtrRepairOrder.WriteElementString("UnitPrice5", txtUnitPrice5.Text)
                wtrRepairOrder.WriteElementString("Quantity5", txtQuantity5.Text)
                wtrRepairOrder.WriteElementString("SubTotal5", txtSubTotal5.Text)
            wtrRepairOrder.WriteElementString("JobDescription1", _
    					  txtJobDescription1.Text)
                wtrRepairOrder.WriteElementString("JobPrice1", txtJobPrice1.Text)
            wtrRepairOrder.WriteElementString("JobDescription2", _
    					  txtJobDescription2.Text)
                wtrRepairOrder.WriteElementString("JobPrice2", txtJobPrice2.Text)
            wtrRepairOrder.WriteElementString("JobDescription3", _
    					  txtJobDescription3.Text)
                wtrRepairOrder.WriteElementString("JobPrice3", txtJobPrice3.Text)
            wtrRepairOrder.WriteElementString("JobDescription4", _
    					  txtJobDescription4.Text)
                wtrRepairOrder.WriteElementString("JobPrice4", txtJobPrice4.Text)
            wtrRepairOrder.WriteElementString("JobDescription5", _
    					  txtJobDescription5.Text)
                wtrRepairOrder.WriteElementString("JobPrice5", txtJobPrice5.Text)
                wtrRepairOrder.WriteElementString("TotalPart", txtTotalParts.Text)
                wtrRepairOrder.WriteElementString("TotalLabor", txtTotalLabor.Text)
                wtrRepairOrder.WriteElementString("TaxRate", txtTaxRate.Text)
                wtrRepairOrder.WriteElementString("TaxAmount", txtTaxAmount.Text)
                wtrRepairOrder.WriteElementString("TotalOrder", txtTotalOrder.Text)
            wtrRepairOrder.WriteElementString("Recommendation", _
    					  txtRecommendations.Text)
    
                wtrRepairOrder.WriteEndElement()
                wtrRepairOrder.WriteEndElement()
    
                wtrRepairOrder.WriteEndDocument()
    
                wtrRepairOrder.Flush()
                wtrRepairOrder.Close()
            End If
    End Sub
  6. Execute the application to test it
  7. Create a new record and click Calculate Order:
     
  8. Click File -> Save and OK to Save the file
  9. Click File -> New Repair Order
  10. Create another repair order:
     
  11. Save it
  12. Close the form and return to your programming environment

Saving a File As XML

If you are creating a text-intensive document and you want to save it as an XML file, for example if you have declared a variable of type TextWriter-derived class (such as StringWriter or StreamWriter), you can use that file to initialize the XmlTextWriter variable. To support TextWriter documents, the XmlTextWriter class is equipped with a constructor with the following syntax:

Public Sub New(w As TextWriter)

This constructor expects as argument a TextWriter-based object. This means that you should have defined the TextWriter object prior to passing it to this constructor. This also implies that the TextWriter was used to specify the encoding scheme that would be used. Here is an example:

Private Sub btnCreate_Click(ByVal sender As Object, _
                                ByVal e As System.EventArgs) _
                                Handles btnCreate.Click
    Dim Filename As String = "students.xml"
    Dim fleStream As FileStream = _
	New FileStream("students.xml", FileMode.Create, _
                       FileAccess.Write, FileShare.None)
    Dim stmWriter As StreamWriter = New StreamWriter(fleStream)
    Dim txtWriter As XmlTextWriter = New XmlTextWriter(stmWriter)

    stmWriter.Flush()
    stmWriter.Close()
End Sub

To actually write the contents of the document, you can create each paragraph by calling the XmlTextWriter.WriteStartElement() method the same way we did earlier. Here is an example:

Private Sub btnCreate_Click(ByVal sender As Object, _
                                ByVal e As System.EventArgs) _
                                Handles btnCreate.Click
        Dim Filename As String = "students.xml"
        Dim fleStream As FileStream = New FileStream("students.xml", _
                      FileMode.Create, _
                      FileAccess.Write, _
                      FileShare.None)
        Dim stmWriter As StreamWriter = New StreamWriter(fleStream)
        Dim txtWriter As XmlTextWriter = New XmlTextWriter(stmWriter)

        txtWriter.WriteStartDocument()
        txtWriter.WriteStartElement("ToAllEmployees")

        For i As Integer = 0 To txtEditor.Lines.Length - 1
            txtWriter.WriteStartElement("Notice")
            txtWriter.WriteString(txtEditor.Lines(i))
            txtWriter.WriteEndElement()
        Next

        txtWriter.WriteEndDocument()

        stmWriter.Flush()
        stmWriter.Close()
End Sub

Reading From an XML File

 

Introduction

Once an XML file exists, you can read it to retrieve the values of its nodes. To support opening an XML file and reading its contents, the .NET Framework provides the XmlTextReader class that is derived from the XmlReader class. The XmlTextReader class is equipped with all the necessary properties and methods to explore the contents of an XML file.

Like XmlTextWriter, the XmlTextReader class reads a file from top to bottom without going back up once it has passed a node:

This means that, when using the XmlTextReader class to read an XML file, once you have read a node and moved down the file, you cannot refer back to the previous node and you cannot access a previous node.

Using and XML Text Reader

To use an XML text reader, declare a variable of type XmlTextReader and initialize it with one of its constructors. The class is equipped with 14 constructors. If you want to open a file whose name or path you know, use the following constructor:

Public Sub New(url As String)

This constructor takes as argument the name of, or path to, an XML file. If the file is found, it would be opened. If the file does not exist or there is an error in the string that specifies its path, the compiler would throw an XmlException exception.

Reading Nodes

After declaring an XmlTextReader variable, you can start reading the content of the file. To support this, you can call the XmlTextReader.Read() method. Its syntax is:

Public Overrides Function Read As Boolean

As mentioned previously, the file is read from top to bottom. Based on this, when you call the Read() method, it reads the first node, moves to the next, and so on until it reaches the end of the file. While reading the file, every time this method reaches a node, you can find out what type of node it is by checking the XmlTextReader.NodeType property. This can help you take a specific action if the reached node meets a certain criterion.

As reviewed in our introductions to XML, each node has a name and possibly a value. You can find out the name of a node by checking the XmlTextReader.Name property. To know the value of a node, retrieve its XmlTextReader.Value property. 

Practical Learning Practical Learning: Reading the Elements of an XML File

  1. Display the form.
    From the Dialogs section of the Toolbox, click OpenFileDialog and click the form
  2. Change its properties as follows:
    Title: Open Existing Repair Order
    DefaultExt: xml
    Filter: Repair Orders (*.xml)|*.xml|All Files|
    Name: dlgOpen
  3. Right-click the form and click View Code
  4. In the Class Name combo box, select mnuFileOpen
  5. In the Method Name combo box, select Click and implement the event as follows:
     
    Private Sub mnuFileOpen_Click(ByVal sender As Object, _
                                      ByVal e As System.EventArgs) _
                                      Handles mnuFileOpen.Click
        Dim rdrRepairOrder As XmlTextReader = Nothing
    
        Try
            If dlgOpen.ShowDialog() = DialogResult.OK Then
                rdrRepairOrder = New XmlTextReader(dlgOpen.FileName)
    
                ' Scan the XML file
                Do
                    ' every time you find an element, find out what type it is
                    ' If you find text, put it in the combo box' list
                    If (XmlNodeType.Element <> 0) And _
                       (rdrRepairOrder.Name = "CustomerName") Then
                        txtCustomerName.Text = _
                        rdrRepairOrder.ReadElementString("CustomerName")
                        txtAddress.Text = rdrRepairOrder.ReadElementString("Addres")
                        txtCity.Text = rdrRepairOrder.ReadElementString("City")
                        txtState.Text = rdrRepairOrder.ReadElementString("State")
                        txtZIPCode.Text = rdrRepairOrder.ReadElementString("ZIPCode")
                        txtMake.Text = rdrRepairOrder.ReadElementString("Make")
                        txtModel.Text = rdrRepairOrder.ReadElementString("Model")
                        txtCarYear.Text = rdrRepairOrder.ReadElementString("CarYear")
                        txtProblem.Text = _
                        rdrRepairOrder.ReadElementString("ProbDescription")
                        txtPartName1.Text = rdrRepairOrder.ReadElementString("PartName1")
                        txtUnitPrice1.Text = rdrRepairOrder.ReadElementString("UnitPrice1")
                        txtQuantity1.Text = rdrRepairOrder.ReadElementString("Quantity1")
                        txtSubTotal1.Text = rdrRepairOrder.ReadElementString("SubTotal1")
                        txtPartName2.Text = rdrRepairOrder.ReadElementString("PartName2")
                        txtUnitPrice2.Text = rdrRepairOrder.ReadElementString("UnitPrice2")
                        txtQuantity2.Text = rdrRepairOrder.ReadElementString("Quantity2")
                        txtSubTotal2.Text = rdrRepairOrder.ReadElementString("SubTotal2")
                        txtPartName3.Text = rdrRepairOrder.ReadElementString("PartName3")
                        txtUnitPrice3.Text = rdrRepairOrder.ReadElementString("UnitPrice3")
                        txtQuantity3.Text = rdrRepairOrder.ReadElementString("Quantity3")
                        txtSubTotal3.Text = rdrRepairOrder.ReadElementString("SubTotal3")
                        txtPartName4.Text = rdrRepairOrder.ReadElementString("PartName4")
                        txtUnitPrice4.Text = rdrRepairOrder.ReadElementString("UnitPrice4")
                        txtQuantity4.Text = rdrRepairOrder.ReadElementString("Quantity4")
                        txtSubTotal4.Text = rdrRepairOrder.ReadElementString("SubTotal4")
                        txtPartName5.Text = rdrRepairOrder.ReadElementString("PartName5")
                        txtUnitPrice5.Text = rdrRepairOrder.ReadElementString("UnitPrice5")
                        txtQuantity5.Text = rdrRepairOrder.ReadElementString("Quantity5")
                        txtSubTotal5.Text = rdrRepairOrder.ReadElementString("SubTotal5")
                        txtJobDescription1.Text = _
                            rdrRepairOrder.ReadElementString("JobDescription1")
                        txtJobPrice1.Text = rdrRepairOrder.ReadElementString("JobPrice1")
                        txtJobDescription2.Text = _
                            rdrRepairOrder.ReadElementString("JobDescription2")
                        txtJobPrice2.Text = rdrRepairOrder.ReadElementString("JobPrice2")
                        txtJobDescription3.Text = _
                            rdrRepairOrder.ReadElementString("JobDescription3")
                        txtJobPrice3.Text = rdrRepairOrder.ReadElementString("JobPrice3")
                        txtJobDescription4.Text = _
                            rdrRepairOrder.ReadElementString("JobDescription4")
                        txtJobPrice4.Text = rdrRepairOrder.ReadElementString("JobPrice4")
                        txtJobDescription5.Text = _
                            rdrRepairOrder.ReadElementString("JobDescription5")
                        txtJobPrice5.Text = rdrRepairOrder.ReadElementString("JobPrice5")
                        txtTotalParts.Text = rdrRepairOrder.ReadElementString("TotalPart")
                        txtTotalLabor.Text = rdrRepairOrder.ReadElementString("TotalLabor")
                        txtTaxRate.Text = rdrRepairOrder.ReadElementString("TaxRate")
                        txtTaxAmount.Text = rdrRepairOrder.ReadElementString("TaxAmount")
                        txtTotalOrder.Text = rdrRepairOrder.ReadElementString("TotalOrder")
                        txtRecommendations.Text = _
                            rdrRepairOrder.ReadElementString("Recommendation")
                    End If
                Loop While rdrRepairOrder.Read()
            End If
        Catch Exc As XmlException
            MsgBox("The file name you provided is not valid")
        Finally
            rdrRepairOrder.Close()
        End Try
    End Sub
  6. Execute the application and open one the previous orders

Details on XML Reading and Writing

 

Indentation

Consider a valid XML file such as the following, opened in Notepad:

Notepad

If you were asked to examine this file, you can see that its crowded words make it difficult to read. To include a white space when writing to the file, you can call the XmlTextWriter.WriteWhiteSpace() method. Its syntax is:

Public Overrides Sub WriteWhitespace(ws As String)

Besides white spaces, indentation consists of setting empty spaces on the left of child nodes to make the file easier to read. Based on this, indentation is not a requirement but a convenience. While the WriteWhiteSpace() method allows you to explicitly create a white space in the file, the XmlTextWriter class is equipped with the Formatting property. This property is a value of the Formatting enumeration. The Formatting enumeration has two members. The Indented value ensures that each child node would be indented from its parent.

If you manually create an XML file, whether using Notepad, Visual Studio, or another text editor, you can indent the nodes as you see fit. To let the compiler know that you want the nodes to be indented, assign the Formatting.Indented member to its Formatting property. Here is an example:

Private Sub btnCreate_Click(ByVal sender As Object, _
                                ByVal e As System.EventArgs) _
                                Handles btnCreate.Click
    Dim Filename As String = "students.xml"
    Dim fleStream As FileStream = _
	New FileStream("students.xml", FileMode.Create, _
                       FileAccess.Write, FileShare.None)
    Dim stmWriter As StreamWriter = New StreamWriter(fleStream)
    Dim txtWriter As XmlTextWriter = New XmlTextWriter(stmWriter)

    Writer.Formatting = Formatting.Indented

    stmWriter.Flush()
    stmWriter.Close()
End Sub

If you manually create an XML file, you can specify the number of empty spaces on the left of a node by pressing the Space bar a few times before typing the node. Most people use 2 or 4 characters for the indentation. If you are programmatically creating the file, to specify the number of characters that should be used during indentation, assign the desired integer to the XmlTextWriter.Indentation property. If you don't use this property, the compiler would use two characters. You can also find out the number of characters used for indentation by retrieving the value of this property.

As mentioned above, indentation consists of entering white spaces on the left of child nodes. Instead of empty spaces, if you want to use another character, assign it to the XmlTextWriter.IndentChar property.

Practical Learning Practical Learning: Indenting XML Nodes

  1. In the Class Name combo box, select mnuFileSave and, to control the indentation when the file is saved, change the top section of the event as follows:
     
    Private Sub mnuFileSave_Click(ByVal sender As Object, _
                                      ByVal e As System.EventArgs) _
                                      Handles mnuFileSave.Click
        . . . No Change
    
        ' Find out if the user clicked OK after displaying the Save dialog box
        If dlgSave.ShowDialog() = DialogResult.OK Then
            Dim wtrRepairOrder As XmlTextWriter = New XmlTextWriter(Filename, _
                        Encoding.UTF8)
            wtrRepairOrder.Formatting = Formatting.Indented
            wtrRepairOrder.Indentation = 4
    
            . . . No Change
        End If
    End Sub
  2. In the Class Name combo box, select mnuFileExit
  3. In the Method Name combo box, select Click and implement the event as follows:
     
    Private Sub mnuFileExit_Click(ByVal sender As Object, _
                                      ByVal e As System.EventArgs) _
                                      Handles mnuFileExit.Click
        End
    End Sub
  4. Execute the application
  5. Create and save a few more repair orders
  6. Close the form

Exercises

 

College Park Auto-Repair

  1. Open the College Park Auto-Repair database from this lesson
  2. Notice that if you open a repair order, change it and try to save it, the application would create a new repair order with a new receipt number.
    Configure the form so that, if a repair order was previous opened then changed, if the user saves it, the current repair order would be saved, using its own receipt number instead of generating a new receipt number

 


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