How to print the content of a RichTextBox control by using Visual Basic .NET or Visual Basic 2005

For a Microsoft Visual Basic 6.0 version of this article, see
146022 .
For a Microsoft Visual C# .NET version of this article, see 812425 .

Summary

This step-by-step article describes how to print the content of a RichTextBox control. The RichTextBox control does not provide a method to print its content. However, you can extend the RichTextBox class to use the EM_FORMATRANGE message. You can then send the content of a RichTextBox to an output device, such as a printer.

Create a RichTextBoxPrintCtrl control

To extend the RichTextBox class and use EM_FORMATRANGE to print the content of the RichTextBox control, follow these steps:
  1. Use Microsoft Visual Basic .NET or Microsoft Visual Basic 2005 to create a new Class Library project named RichTextBoxPrintCtrl.

    By default, Class1.vb is created.
  2. Change the name of the Class1.vb file to
    RichTextBoxPrintCtrl.vb.
  3. In the Solution Explorer, right-click
    References, and then click Add Reference.
  4. In the Add Reference dialog box, double-click System.Drawing.dll, and then double-click System.Windows.Forms.dll.
  5. To add references, click OK.
  6. Delete the existing code in
    RichTextBoxPrintCtrl.vb.
  7. Copy the following code to
    RichTextBoxPrintCtrl.vb:
    Option Explicit On 

    Imports System
    Imports System.Windows.Forms
    Imports System.Drawing
    Imports System.Runtime.InteropServices
    Imports System.Drawing.Printing

    Namespace RichTextBoxPrintCtrl
    Public Class RichTextBoxPrintCtrl
    Inherits RichTextBox
    ' Convert the unit that is used by the .NET framework (1/100 inch)
    ' and the unit that is used by Win32 API calls (twips 1/1440 inch)
    Private Const AnInch As Double = 14.4

    <StructLayout(LayoutKind.Sequential)> _
    Private Structure RECT
    Public Left As Integer
    Public Top As Integer
    Public Right As Integer
    Public Bottom As Integer
    End Structure

    <StructLayout(LayoutKind.Sequential)> _
    Private Structure CHARRANGE
    Public cpMin As Integer ' First character of range (0 for start of doc)
    Public cpMax As Integer ' Last character of range (-1 for end of doc)
    End Structure

    <StructLayout(LayoutKind.Sequential)> _
    Private Structure FORMATRANGE
    Public hdc As IntPtr ' Actual DC to draw on
    Public hdcTarget As IntPtr ' Target DC for determining text formatting
    Public rc As Rect ' Region of the DC to draw to (in twips)
    Public rcPage As Rect ' Region of the whole DC (page size) (in twips)
    Public chrg As CHARRANGE ' Range of text to draw (see above declaration)
    End Structure

    Private Const WM_USER As Integer = &H400
    Private Const EM_FORMATRANGE As Integer = WM_USER + 57

    Private Declare Function SendMessage Lib "USER32" Alias "SendMessageA" (ByVal hWnd As IntPtr, ByVal msg As Integer, ByVal wp As IntPtr, ByVal lp As IntPtr) As IntPtr

    ' Render the contents of the RichTextBox for printing
    'Return the last character printed + 1 (printing start from this point for next page)
    Public Function Print(ByVal charFrom As Integer, ByVal charTo As Integer, ByVal e As PrintPageEventArgs) As Integer

    ' Mark starting and ending character
    Dim cRange As CHARRANGE
    cRange.cpMin = charFrom
    cRange.cpMax = charTo

    ' Calculate the area to render and print
    Dim rectToPrint As RECT
    rectToPrint.Top = e.MarginBounds.Top * AnInch
    rectToPrint.Bottom = e.MarginBounds.Bottom * AnInch
    rectToPrint.Left = e.MarginBounds.Left * AnInch
    rectToPrint.Right = e.MarginBounds.Right * AnInch

    ' Calculate the size of the page
    Dim rectPage As RECT
    rectPage.Top = e.PageBounds.Top * AnInch
    rectPage.Bottom = e.PageBounds.Bottom * AnInch
    rectPage.Left = e.PageBounds.Left * AnInch
    rectPage.Right = e.PageBounds.Right * AnInch

    Dim hdc As IntPtr = e.Graphics.GetHdc()

    Dim fmtRange As FORMATRANGE
    fmtRange.chrg = cRange ' Indicate character from to character to
    fmtRange.hdc = hdc ' Use the same DC for measuring and rendering
    fmtRange.hdcTarget = hdc ' Point at printer hDC
    fmtRange.rc = rectToPrint ' Indicate the area on page to print
    fmtRange.rcPage = rectPage ' Indicate whole size of page

    Dim res As IntPtr = IntPtr.Zero

    Dim wparam As IntPtr = IntPtr.Zero
    wparam = New IntPtr(1)

    ' Move the pointer to the FORMATRANGE structure in memory
    Dim lparam As IntPtr = IntPtr.Zero
    lparam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange))
    Marshal.StructureToPtr(fmtRange, lparam, False)

    ' Send the rendered data for printing
    res = SendMessage(Handle, EM_FORMATRANGE, wparam, lparam)

    ' Free the block of memory allocated
    Marshal.FreeCoTaskMem(lparam)

    ' Release the device context handle obtained by a previous call
    e.Graphics.ReleaseHdc(hdc)

    ' Return last + 1 character printer
    Return res.ToInt32()
    End Function

    End Class
    End Namespace
  8. To create RichTextBoxPrintCtrl.dll, click
    Build Solution on the Build menu.

Test the control

To test the control, follow these steps:
  1. Create a new Windows Application project by using Visual Basic .NET or Visual Basic 2005.

    By default, Form1.vb is created.
  2. From the Toolbox, drag a button onto Form1. Change the Name to btnPageSetup, and change the Text to Page Setup.
  3. From the Toolbox, drag another button onto Form1. Change the Name to btnPrintPreview, and change the Text to
    Print Preview.
  4. From the Toolbox, drag another button onto Form1. Change the Name to btnPrint, and change the Text to
    Print.
  5. In the Toolbox, double-click PrintDialog, double-click PrintPreviewDialog, double-click
    PrintDocument, and then double-click
    PageSetupDialog to add these controls to Form1.
  6. Modify the Document property of PrintDialog1,
    PrintPreviewDialog1, and PageSetupDialog1 to
    PrintDocument1.
  7. On the Tools menu, click Customize Toolbox.
  8. Click .NET Framework Components, click
    Browse, click to select
    RichTextBoxPrintCtrl.dll, and then click
    OK.
  9. From the Toolbox, drag
    RichTextBoxPrintCtrl onto Form1.
  10. In the Solution Explorer, right-click
    Form1.vb, and then click View Code.
  11. Add the following code to Class Form1:
       Private checkPrint As Integer

    Private Sub PrintDocument1_BeginPrint(ByVal sender As Object, ByVal e As System.Drawing.Printing.PrintEventArgs) Handles PrintDocument1.BeginPrint
    checkPrint = 0
    End Sub

    Private Sub PrintDocument1_PrintPage(ByVal sender As Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) Handles PrintDocument1.PrintPage
    ' Print the content of the RichTextBox. Store the last character printed.
    checkPrint = RichTextBoxPrintCtrl1.Print(checkPrint, RichTextBoxPrintCtrl1.TextLength, e)

    ' Look for more pages
    If checkPrint < RichTextBoxPrintCtrl1.TextLength Then
    e.HasMorePages = True
    Else
    e.HasMorePages = False
    End If
    End Sub

    Private Sub btnPageSetup_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPageSetup.Click.Click
    PageSetupDialog1.ShowDialog()
    End Sub

    Private Sub btnPrint_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPrint.Click
    If PrintDialog1.ShowDialog() = DialogResult.OK Then
    PrintDocument1.Print()
    End If
    End Sub

    Private Sub btnPrintPreview_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPrintPreview.Click
    PrintPreviewDialog1.ShowDialog()
    End Sub
  12. To run the application, click Start on the
    Debug menu.
  13. Type text in
    RichTextBoxPrintCtrl.
  14. To set the page settings, click Page Setup.
  15. To see a preview of the page, click Print Preview.
  16. To print the content of the
    RichTextBoxPrintCtrl, click Print.

References

For more information, visit the Microsoft .NET Framework Software Development Kit (SDK) Documentation or the following MSDN online Help Web site:
Propriedades

ID do Artigo: 811401 - Última Revisão: 13 de nov de 2007 - Revisão: 1

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