CSharp打印功能的实现

本分步指南介绍了如何打印RichTextBox 控件的内容。RichTextBox 控件没有提供任何打印RichTextBox 内容的方法。您可以扩展RichTextBox 类以使用EM_FORMATRANGE 消息将RichTextBox 控件的内容发送到一个输出设备（如打印机）。

创建RichTextBoxPrintCtrl 控件

下面的示例介绍了如何扩展RichTextBox 类，以及如何使用EM_FORMATRANGE 打印RichTextBox 控件的内容。

1、在Visual C# .NET 中，新建一个名为RichTextBoxPrintCtrl 的类库项目。默认情况下创建Class1.cs。

2、将Class1.cs 的名称改为RichTextBoxPrintCtrl.cs。

3、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”。

4、在“添加引用”对话框中，双击“System.Drawing.dll”和“System.Windows.Forms.dll”，然后单击“确定”。

5、将RichTextBoxPrintCtl.cs 中的现有代码替换为以下代码：

using System;

using System.Windows.Forms;

using System.Drawing;

using System.Runtime.InteropServices;

using System.Drawing.Printing;

namespace RichTextBoxPrintCtrl

{

public class RichTextBoxPrintCtrl:RichTextBox

{

//Convert the unit used by the .NET framework (1/100 inch)

//and the unit used by Win32 API calls (twips 1/1440 inch)

private const double anInch = 14.4;

[StructLayout(LayoutKind.Sequential)]

private struct RECT

{

public int Left;

public int Top;

public int Right;

public int Bottom;

}

[StructLayout(LayoutKind.Sequential)]

private struct CHARRANGE

{

public int cpMin; //First character of range (0 for start of doc)

public int cpMax; //Last character of range (-1 for end of doc)

}

[StructLayout(LayoutKind.Sequential)]

private struct FORMATRANGE

{

public IntPtr hdc; //Actual DC to draw on

public IntPtr hdcTarget; //Target DC for determining text formatting

public RECT rc; //Region of the DC to draw to (in twips)

public RECT rcPage; //Region of the whole DC (page size) (in twips)

public CHARRANGE chrg; //Range of text to draw (see earlier declaration)

}

private const int WM_USER = 0x0400;

private const int EM_FORMATRANGE = WM_USER + 57;

[DllImport("USER32.dll")]

private static extern IntPtr SendMessage (IntPtr hWnd , int msg , IntPtr wp, IntPtr lp);

// Render the contents of the RichTextBox for printing

// Return the last character printed + 1 (printing start from this point for next page)

public int Print( int charFrom, int charTo,PrintPageEventArgs e)

{

//Calculate the area to render and print

RECT rectToPrint;

rectToPrint.Top = (int)(e.MarginBounds.Top * anInch);

rectToPrint.Bottom = (int)(e.MarginBounds.Bottom * anInch);

rectToPrint.Left = (int)(e.MarginBounds.Left * anInch);

rectToPrint.Right = (int)(e.MarginBounds.Right * anInch);

//Calculate the size of the page

RECT rectPage;

rectPage.Top = (int)(e.PageBounds.Top * anInch);

rectPage.Bottom = (int)(e.PageBounds.Bottom * anInch);

rectPage.Left = (int)(e.PageBounds.Left * anInch);

rectPage.Right = (int)(e.PageBounds.Right * anInch);

IntPtr hdc = e.Graphics.GetHdc();

FORMATRANGE fmtRange;

fmtRange.chrg.cpMax = charTo; //Indicate character from to character to

fmtRange.chrg.cpMin = charFrom;

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 size of page

IntPtr res = IntPtr.Zero;

IntPtr wparam = IntPtr.Zero;

wparam = new IntPtr(1);

//Get the pointer to the FORMATRANGE structure in memory

IntPtr lparam= IntPtr.Zero;

lparam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange));

Marshal.StructureToPtr(fmtRange, lparam, false);

//Send the rendered data for printing

res = SendMessage(Handle, EM_FORMA TRANGE, 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();

}

}

}

6、在“生成”菜单中，单击“生成解决方案”以创建RichTextBoxPrintCtrl.dll。

测试控件

1、在Visual C# .NET 中创建一个新的Windows 应用程序项目。默认情况下将创建出Form1.cs。

2、将一个按钮控件从工具箱拖入Form1。将Name 属性更改为btnPageSetup，并将Text 属性更改为页面设置。

3、将另一个按钮控件从工具箱拖入Form1。将Name 属性更改为btnPrintPreview，并将Text 属性更改为打印预览。

4、将另一个按钮控件从工具箱拖入Form1。将Name 属性更改为btnPrint，并将Text 属性更改为打印。

5、在工具箱中，双击“PrintDialog”、“PrintPreviewDialog”、“PrintDocument”和“PageSetupDialog”以将这些控件添加到Form1 中。

6、将PrintDialog1、PrintPreviewDialog1 和PageSetupDialog1 控件的Document 属性修改为PrintDocument1。

7、在“工具”菜单上，单击“自定义工具箱”。

8、在“.NET Framework 组件”选项卡上，单击“浏览”，单击以选中“RichTextBoxPrintCtrl.dll”，然后单击“确定”。

9、将RichTextBoxPrintCtrl 从工具箱拖入Form1。

10、在解决方案资源管理器中，右键单击Form1.cs，然后单击查看代码。

11、将以下代码添加到InitializeComponent 方法中：

this.printDocument1.BeginPrint += new System.Drawing.Printing.PrintEventHandler

(this.printDocument1_BeginPrint);

this.printDocument1.PrintPage += new System.Drawing.Printing.PrintPageEvent Handler(this.printDocument1_PrintPage);

this.btnPrint.Click += new System.EventHandler(this.btnPrint_Click);

this.btnPrintPreview.Click += new System.EventHandler(this.btnPrintPreview_Click);

this.btnPageSetup.Click += new System.EventHandler(this.btnPageSetup_Click);

12、将下面的代码添加到Form1 类：

private int checkPrint;

private void btnPageSetup_Click(object sender, System.EventArgs e)

{

pageSetupDialog1.ShowDialog();

}

private void btnPrintPreview_Click(object sender, System.EventArgs e)

{

printPreviewDialog1.ShowDialog();

}

private void btnPrint_Click(object sender, System.EventArgs e)

{

if (printDialog1.ShowDialog() == DialogResult.OK)

printDocument1.Print();

}

private void printDocument1_BeginPrint(object sender, System.Drawing.Printing.PrintEventArgs e)

{

checkPrint = 0;

}

private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)

{

// Print the content of RichTextBox. Store the last character printed.

checkPrint = richTextBoxPrintCtrl1.Print(checkPrint, richTextBoxPrintCtrl1.TextLength, e);

// Check for more pages

if (checkPrint < richTextBoxPrintCtrl1.TextLength)

e.HasMorePages = true;

else

e.HasMorePages = false;

}

13、在“调试”菜单上，单击“启动”以运行该应用程序。Form1 将显示出来。

14、在RichTextBoxPrintCtrl 中键入一些文本。

15、单击“页面设置”以设置页面设置。

16、单击“打印预览”以查看页面的打印预览。

17、单击“打印”以打印“RichTextBoxPrintCtrl”的内容。