SelPrint 属性未升级
在 Visual Basic 6.0 中，RichTextBox 控件的 SelPrint 方法可用于打印该控件的内容。它采用单一参数 hDC，该参数指定设备的设备上下文。
在 Visual Basic 2008 中，不再存在 SelPrint 方法，设备上下文也不再用于打印。RichTextBox 控件不提供打印其内容的方法。但是，您可以扩展 RichTextBox 类以使用 EM_FORMATRANGE 消息。然后，可以将 RichTextBox 的内容发送到输出设备，如打印机。用于完成此过程的两个步骤为：
创建一个从 RichTextBox 继承的 RichTextBoxPrintCtrl 类。
在升级后的项目中使用 RichTextBoxPrintCtrl 类。
创建从 RichTextBox 类继承的类
使用 Visual Basic 2008 创建一个名为 RichTextBoxPrintCtrl 的新“类库”项目。
默认情况下，创建 Class1.vb。
将 Class1.vb 文件的名称更改为 RichTextBoxPrintCtrl.vb。
在“解决方案资源管理器”中，右键单击“引用”，然后单击“添加引用”。
在“添加引用”对话框中，双击“System.Drawing.dll”，然后双击“System.Windows.Forms.dll”。
要添加引用，请单击“确定”。
删除 RichTextBoxPrintCtrl.vb 中现有的代码。
将下列代码复制到 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 Private WithEvents m_PrintDocument As Printing.PrintDocument Private intCharactersToPrint As Integer Private intCurrentPosition As Integer <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 ' First character of range (0 for start of doc) Public cpMin As Integer ' Last character of range (-1 for end of doc) Public cpMax As Integer End Structure <StructLayout(LayoutKind.Sequential)> _ Private Structure FORMATRANGE ' Actual DC to draw on Public hdc As IntPtr ' Target DC for determining text formatting Public hdcTarget As IntPtr ' Region of the DC to draw to (in twips) Public rc As Rect ' Region of the whole DC (page size) (in twips) Public rcPage As Rect ' Range of text to draw (see above declaration) Public chrg As CHARRANGE 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 Public Sub SelPrint() 'print only the selected text if any is selected If Me.SelectionLength > 0 Then intCharactersToPrint = Me.SelectionStart + Me.SelectionLength intCurrentPosition = Me.SelectionStart Else 'otherwise print the entire document intCharactersToPrint = Me.TextLength intCurrentPosition = 0 End If m_PrintDocument.Print() End Sub ' Render the contents of the RichTextBox for printing ' Return the last character printed + 1 (printing start from ' this point for next page) Private 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 ' Indicate character from to character to fmtRange.chrg = cRange ' Use the same DC for measuring and rendering fmtRange.hdc = hdc ' Point at printer hDC fmtRange.hdcTarget = hdc ' Indicate the area on page to print fmtRange.rc = rectToPrint ' Indicate whole size of page fmtRange.rcPage = rectPage 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 the last + 1 character printed Return res.ToInt32 End Function Public ReadOnly Property PrintDocument() As Printing.PrintDocument Get If m_PrintDocument Is Nothing Then m_PrintDocument = New Printing.PrintDocument End If Return m_PrintDocument End Get End Property Private Sub m_PrintDocument_PrintPage(ByVal sender As _ Object, ByVal e As System.Drawing.Printing.PrintPageEventArgs) _ Handles m_PrintDocument.PrintPage ' Print the content of the RichTextBox. ' Store the last character printed. intCurrentPosition = Me.Print(intCurrentPosition, _ intCharactersToPrint, e) ' Look for more pages by checking If intCurrentPosition < intCharactersToPrint Then e.HasMorePages = True Else e.HasMorePages = False End If End Sub End Class End Namespace要创建 RichTextBoxPrintCtrl.dll，请单击“生成”菜单上的“生成解决方案”。
在升级后的项目中使用 RichTextBoxPrintCtrl 类
在 Visual Basic 2008 中打开升级后的 Windows 应用程序项目。
从“工具箱”中，将 PrintDialog 组件拖动到包含 RichTextBox 控件的窗体中。
在“工具”菜单上，单击“自定义工具箱”。
单击“.NET Framework 组件”，单击“浏览”，单击以选择“RichTextBoxPrintCtrl.dll”，然后单击“确定”。
将一个 RichTextBoxPrintCtrl 从“工具箱”中拖动到窗体上。
将 RichTextBoxPrintCtrl 的属性设置为与您的原始 RichTextBox 控件的属性相匹配。
删除 RichTextBox 控件，然后将 RichTextBoxPrintCtrl 控件重命名为您的原始 RichTextBox 控件的名称。
双击此窗体以打开代码编辑器。
在 Button_Click 事件处理程序（或在原始代码中调用 SelPrint 的位置）中添加以下代码：
' NOTE: Replace "Button1" with the name of your actual Print button Private Sub Button1_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles Button1.Click 'associate the correct printdocument to the printdialog PrintDialog1.Document = Me.RichTextBoxPrintCtrl1.PrintDocument If PrintDialog1.ShowDialog() = DialogResult.OK Then Me.RichTextBoxPrintCtrl1.SelPrint() End If End Sub