如何在C#中实现打印功能？

在C#中使用PrintDialog可以很方便的实现程序的打印功能。

其步骤如下：

1. 创建一个PrintDialog的实例。如下：
   System.Windows.Forms.PrintDialog PrintDialog1=new PrintDialog ();
2. 创建一个PrintDocument的实例.如下：
   System.Drawing.Printing.PrintDocument docToPrint =
   new System.Drawing.Printing.PrintDocument();
3. 设置打印机开始打印的事件处理函数.函数原形如下：
   void docToPrint_PrintPage(object sender,
   System.Drawing.Printing.PrintPageEventArgs e)
4. 将事件处理函数添加到PrintDocument的PrintPage事件中。
   docToPrint.PrintPage+=new PrintPageEventHandler(docToPrint_PrintPage);
5. 设置PrintDocument的相关属性，如：
   PrintDialog1.AllowSomePages = true;PrintDialog1.ShowHelp = true;
6. 把PrintDialog的Document属性设为上面配置好的PrintDocument的实例：
   PrintDialog1.Document = docToPrint;
7. 调用PrintDialog的ShowDialog函数显示打印对话框：
   DialogResult result = PrintDialog1.ShowDialog();
8. 根据用户的选择，开始打印：
   if (result==DialogResult.OK)
   {
   docToPrint.Print();
   }

   using System;
   using System.Drawing.Printing;
   using System.Windows.Forms;
   using System.IO;

   namespace EDImageSystem
   {
   /// <summary>
   /// PrintService 的摘要说明。
   /// </summary>
   public class PrintService
   {
   public PrintService()
   {
   //
   // TODO: 在此处添加构造函数逻辑
   //
   this.docToPrint.PrintPage+=new PrintPageEventHandler(docToPrint_PrintPage);
   }//将事件处理函数添加到PrintDocument的PrintPage中

   // Declare the PrintDocument object.
   private System.Drawing.Printing.PrintDocument docToPrint =
   new System.Drawing.Printing.PrintDocument();//创建一个PrintDocument的实例

   private System.IO.Stream streamToPrint;
   string streamType;

   // This method will set properties on the PrintDialog object and
   // then display the dialog.
   public void StartPrint(Stream streamToPrint,string streamType)
   {

   this.streamToPrint=streamToPrint;
   this.streamType=streamType;
   // Allow the user to choose the page range he or she would
   // like to print.
   System.Windows.Forms.PrintDialog PrintDialog1=new PrintDialog ();//创建一个PrintDialog的实例。
   PrintDialog1.AllowSomePages = true;

   // Show the help button.
   PrintDialog1.ShowHelp = true;

   // Set the Document property to the PrintDocument for
   // which the PrintPage Event has been handled. To display the
   // dialog, either this property or the PrinterSettings property
   // must be set
   PrintDialog1.Document = docToPrint;//把PrintDialog的Document属性设为上面配置好的PrintDocument的实例

   DialogResult result = PrintDialog1.ShowDialog();//调用PrintDialog的ShowDialog函数显示打印对话框

   // If the result is OK then print the document.
   if (result==DialogResult.OK)
   {
   docToPrint.Print();//开始打印
   }

   }

   // The PrintDialog will print the document
   // by handling the document’s PrintPage event.
   private void docToPrint_PrintPage(object sender,
   System.Drawing.Printing.PrintPageEventArgs e)//设置打印机开始打印的事件处理函数
   {

   // Insert code to render the page here.
   // This code will be called when the control is drawn.

   // The following code will render a simple
   // message on the printed document
   switch(this.streamType)
   {
   case "txt":
   string text = null;
   System.Drawing.Font printFont = new System.Drawing.Font
   ("Arial", 35, System.Drawing.FontStyle.Regular);

   // Draw the content.
   System.IO.StreamReader streamReader=new StreamReader(this.streamToPrint);
   text=streamReader.ReadToEnd();
   e.Graphics.DrawString(text,printFont,System.Drawing.Brushes.Black,e.MarginBounds.X,e.MarginBounds.Y);
   break;
   case "image":
   System.Drawing.Image image=System.Drawing.Image.FromStream(this.streamToPrint);
   int x=e.MarginBounds.X;
   int y=e.MarginBounds.Y;
   int width=image.Width;
   int height=image.Height;
   if((width/e.MarginBounds.Width)>(height/e.MarginBounds.Height))
   {
   width=e.MarginBounds.Width;
   height=image.Height*e.MarginBounds.Width/image.Width;
   }
   else
   {
   height=e.MarginBounds.Height;
   width=image.Width*e.MarginBounds.Height/image.Height;
   }
   System.Drawing.Rectangle destRect=new System.Drawing.Rectangle(x,y,width,height);
   e.Graphics.DrawImage(image,destRect,0,0,image.Width,image.Height,System.Drawing.GraphicsUnit.Pixel);
   break;
   default:
   break;
   }
   
   }

   }
   }

例子如下：

使用时先创建PrintService类的实例，然后调用void StartPrint(Stream streamToPrint,string streamType)函数开始打樱其中streamToPrint是要打印的内容（字节流），streamType是流的类型（txt表示普通文本，image表示图像）；