VB.NET中如何在PrintDialog对话框内实现打印预览？

我在VB.NET里想让PrintDialog对话框自带打印预览功能，但预览区域一直显示**"This app doesn't support print preview"**（如下图）。目前打印功能能正常运行，但搜到的解决方案全是让用PrintPreviewDialog，这不是我想要的实现方式。

我的相关代码如下：

打印触发方法 #

Private Sub PrintReplacementCostReport(Optional ByVal Title As String = "Replacement Cost Report")

  Dim Caller As String = GetCurrentMethod.DeclaringType.Name & "." & GetCurrentMethod.Name
  'ClsDebug.LogProcEnter(New StackFrame(0, True).GetFileLineNumber, Caller)

  ClearErrorMessage()

  m_PageTitle = "Replacement Cost Report"
  ModGlobals.ReportRichTextBox = Me.rtfReport

  If Me.rtfReport.Lines.Count > 0 Then

     _currentRecord = 1 '-- Skip the heading

     SetPrintDocumentCommonSettings(m_PageTitle)
     SetPrintDialogCommonSettings()

     If PrintDialog1.ShowDialog = DialogResult.OK Then

        ClearErrorMessage()

        PrintDocument1.Print()

     End If

     ClearErrorMessage()

  Else
     If m_PageTitle = "Replacement Cost Report" Then

        Report("You Must Run a [Replacement Cost] Report Before Printing")
     End If
  End If

  'ClsDebug.LogProcExit(New StackFrame(0, True).GetFileLineNumber, Caller)
End Sub

PrintDialog配置方法 #

Private Sub SetPrintDialogCommonSettings(Optional ByVal ToFile As Boolean = False)

  With PrintDialog1
     .Document = PrintDocument1

     .PrinterSettings = PrintDocument1.PrinterSettings

     .AllowSomePages = True
     .AllowSelection = True
     .AllowPrintToFile = True
     .AllowCurrentPage = True

     If ToFile Then
        .PrinterSettings.PrinterName = "Microsoft Print to PDF"
        .PrintToFile = True
        .PrinterSettings.PrintFileName = "PrintDialogToFile.pdf"
     End If
  End With
End Sub

PrintDocument配置方法 #

Private Sub SetPrintDocumentCommonSettings(ByVal Title As String,
                                          Optional ByVal ToFile As Boolean = False,
                                          Optional ByVal ToFileName As String = "")

  With PrintDocument1
     .DocumentName = Title

     .PrinterSettings.Copies = 1
     .PrinterSettings.PrintToFile = True


     .DefaultPageSettings.Margins.Right = 50
     .DefaultPageSettings.Margins.Left = 50
     .DefaultPageSettings.Margins.Top = 50
     .DefaultPageSettings.Margins.Bottom = 50

     If ToFile Then
        .DefaultPageSettings.PrinterSettings.PrintToFile = True
        .DefaultPageSettings.PrinterSettings.PrinterName = "Microsoft Print to PDF"
        .DefaultPageSettings.PrinterSettings.PrintFileName = "Roosevelt Dimes.pdf"

     End If

     .PrinterSettings.DefaultPageSettings.Margins.Left = 30 '50
     .PrinterSettings.DefaultPageSettings.Margins.Right = 30 '50

     .PrinterSettings.DefaultPageSettings.Margins.Top = 50
     .PrinterSettings.DefaultPageSettings.Margins.Bottom = 50

     yPos = .PrinterSettings.DefaultPageSettings.Margins.Top
  End With

  m_RememberSubTitle = String.Empty
  m_RememberTitle = String.Empty
  ModGlobals.WhiteSpace = False

  m_Landscape = False

  _PageChanged = True
  _currentPage = 0
End Sub

解决方案 #

首先明确：.NET WinForms原生的PrintDialog本身并不自带预览功能，你看到的预览区域是系统级打印对话框的一部分，它需要应用程序提供完整的打印渲染逻辑，且依赖打印机驱动支持才能显示预览。

具体修复步骤： #

1. 完善PrintDocument的PrintPage事件实现
   系统预览完全依赖这个事件的渲染逻辑生成预览内容，你的代码里没贴这部分，这大概率是预览失效的核心原因。示例实现（适配你的RichTextBox内容）：

Private Sub PrintDocument1_PrintPage(sender As Object, e As Printing.PrintPageEventArgs) Handles PrintDocument1.PrintPage
    ' 从RichTextBox获取内容并渲染到打印画布
    Dim content As String = ModGlobals.ReportRichTextBox.Text
    Dim printFont As New Font("Arial", 10)
    Dim lineHeight As Single = printFont.GetHeight(e.Graphics)
    Dim yPosition As Single = e.MarginBounds.Top

    ' 逐行绘制内容
    For Each line As String In content.Split(vbCrLf)
        If yPosition + lineHeight > e.MarginBounds.Bottom Then
            e.HasMorePages = True
            Return
        End If
        e.Graphics.DrawString(line, printFont, Brushes.Black, e.MarginBounds.Left, yPosition)
        yPosition += lineHeight
    Next
    e.HasMorePages = False
End Sub

2. 启用系统增强型打印对话框
   修改SetPrintDialogCommonSettings方法，开启UseEXDialog属性，让PrintDialog调用系统增强版对话框，提升预览兼容性：

Private Sub SetPrintDialogCommonSettings(Optional ByVal ToFile As Boolean = False)
    With PrintDialog1
        .Document = PrintDocument1
        .PrinterSettings = PrintDocument1.PrinterSettings
        .AllowSomePages = True
        .AllowSelection = True
        .AllowPrintToFile = True
        .AllowCurrentPage = True
        .UseEXDialog = True ' 启用系统增强对话框，优化预览支持
        If ToFile Then
            .PrinterSettings.PrinterName = "Microsoft Print to PDF"
            .PrintToFile = True
            .PrinterSettings.PrintFileName = "PrintDialogToFile.pdf"
        End If
    End With
End Sub

3. 额外注意点

• 部分打印机驱动本身不支持系统级预览，即使代码正确也可能显示不支持提示，这种情况只能换用PrintPreviewDialog。
• 如果上述方法仍无效，.NET WinForms目前没有官方方案让PrintDialog强制显示预览，只能考虑自定义一个包含预览和打印选项的复合对话框。

内容的提问来源于stack exchange，提问作者E Bell