如何给另外一个进程发送消息？

比如，启动一个计算器，然后，发送3，*,8，最后在计算器上显示24。

参考文章：

int   wm_keydown   =   0x100;  
            foreach   (   process   p   in   process.getprocesses(system.environment.machinename)   )    
              {   intptr   handle   =   p.mainwindowhandle;  
     
                      if(p.startinfo.filename=="calc.exe")    
     
                      {    
  sendmessage(handle,wm_keydown,0,keys.numpad1);  
                                }    
     
   
   
  [dllimport("user32.dll",   charset=charset.auto)]  
  public   static   extern   intptr   sendmessage(intptr   hwnd,   int   umsg,   int   wparam,   int   lparam);

1.启动计算器，得到  
  2.获得活动窗口的线程号,获得与自己程序的窗口相关的线程号  
  3.将两个线程的输入联系起来  
  4，sendkey  
  5.线程分离.  
  这是以前作的一个例子，有一些对你的这个问题没有用，自己挑挑吧。在我的计算机上已经运行通过，看到那个24了。  
   
   
  using   system;  
  using   system.drawing;  
  using   system.collections;  
  using   system.componentmodel;  
  using   system.windows.forms;  
  using   system.data;  
  using   system.runtime.interopservices;  
  using   system.text;  
  using   system.diagnostics;  
   
  namespace   activewindow  
  {  
  ///   <summary>  
  ///   summary   description   for   form1.  
  ///   </summary>  
  public   class   form1   :   system.windows.forms.form  
  {  
  [dllimport("user32.dll")]  
  private   static   extern   int   getwindowtext(intptr   hwnd,   stringbuilder   title,   int   size);  
   
  [   dllimport("user32.dll")   ]  
  private   static   extern   intptr   getforegroundwindow();  
   
  [dllimport("user32.dll")]    
  private   static   extern   intptr   getwindowthreadprocessid(intptr   hwnd,   intptr   processid);  
   
  [dllimport("user32.dll")]    
  private   static   extern   intptr   attachthreadinput(intptr   idattach,   intptr   idattachto,   int   fattach);  
   
  [dllimport("user32.dll")]    
  private   static   extern   intptr   getfocus();  
   
  private   system.windows.forms.label   label1;  
  private   system.windows.forms.label   label2;  
  private   system.windows.forms.label   label3;  
  private   system.windows.forms.label   captionwindowlabel;  
  private   system.windows.forms.label   idwindowlabel;  
  private   system.windows.forms.button   button1;  
  private   system.windows.forms.timer   timer1;  
  private   system.windows.forms.button   button2;  
  private   system.componentmodel.icontainer   components;  
   
  private   void   getactivewindow()  
  {  
  process   p   =   process.start("calc.exe");  
  intptr   activewindowhandle   =   p.mainwindowhandle;  
       
  //获得活动窗口的线程号  
  intptr   handle1   =   getwindowthreadprocessid(this.handle,intptr.zero);  
  intptr   handle2   =   getwindowthreadprocessid(activewindowhandle,intptr.zero);  
  if   (activewindowhandle   !=   this.handle)  
  {  
  //将两个线程的输入联系起来  
  attachthreadinput(handle1,handle2,1);  
  sendkeys.send("3");  
  sendkeys.send("*");  
  sendkeys.send("8");  
  sendkeys.send("=");  
   
  //线程分离  
  attachthreadinput(handle1,handle2,0);  
   
   
  }  
   
  }  
   
   
  public   form1()  
  {  
  //  
  //   required   for   windows   form   designer   support  
  //  
  initializecomponent();  
   
  //  
  //   todo:   add   any   constructor   code   after   initializecomponent   call  
  //  
  }  
   
  ///   <summary>  
  ///   clean   up   any   resources   being   used.  
  ///   </summary>  
  protected   override   void   dispose(   bool   disposing   )  
  {  
  if(   disposing   )  
  {  
  if   (components   !=   null)    
  {  
  components.dispose();  
  }  
  }  
  base.dispose(   disposing   );  
  }  
   
  #region   windows   form   designer   generated   code  
  ///   <summary>  
  ///   required   method   for   designer   support   -   do   not   modify  
  ///   the   contents   of   this   method   with   the   code   editor.  
  ///   </summary>  
  private   void   initializecomponent()  
  {  
  this.components   =   new   system.componentmodel.container();  
  this.label1   =   new   system.windows.forms.label();  
  this.label2   =   new   system.windows.forms.label();  
  this.label3   =   new   system.windows.forms.label();  
  this.captionwindowlabel   =   new   system.windows.forms.label();  
  this.idwindowlabel   =   new   system.windows.forms.label();  
  this.button1   =   new   system.windows.forms.button();  
  this.timer1   =   new   system.windows.forms.timer(this.components);  
  this.button2   =   new   system.windows.forms.button();  
  this.suspendlayout();  
  //    
  //   label1  
  //    
  this.label1.location   =   new   system.drawing.point(174,   9);  
  this.label1.name   =   "label1";  
  this.label1.size   =   new   system.drawing.size(143,   19);  
  this.label1.tabindex   =   0;  
  this.label1.text   =   "active   window   detail";  
  //    
  //   label2  
  //    
  this.label2.location   =   new   system.drawing.point(20,   46);  
  this.label2.name   =   "label2";  
  this.label2.size   =   new   system.drawing.size(123,   19);  
  this.label2.tabindex   =   1;  
  this.label2.text   =   "window   caption   :   ";  
  //    
  //   label3  
  //    
  this.label3.location   =   new   system.drawing.point(20,   102);  
  this.label3.name   =   "label3";  
  this.label3.size   =   new   system.drawing.size(123,   18);  
  this.label3.tabindex   =   2;  
  this.label3.text   =   "window   handle   :";  
  //    
  //   captionwindowlabel  
  //    
  this.captionwindowlabel.location   =   new   system.drawing.point(143,   46);  
  this.captionwindowlabel.name   =   "captionwindowlabel";  
  this.captionwindowlabel.size   =   new   system.drawing.size(287,   47);  
  this.captionwindowlabel.tabindex   =   3;  
  //    
  //   idwindowlabel  
  //    
  this.idwindowlabel.location   =   new   system.drawing.point(143,   102);  
  this.idwindowlabel.name   =   "idwindowlabel";  
  this.idwindowlabel.size   =   new   system.drawing.size(128,   18);  
  this.idwindowlabel.tabindex   =   4;  
  //    
  //   button1  
  //    
  this.button1.location   =   new   system.drawing.point(225,   148);  
  this.button1.name   =   "button1";  
  this.button1.size   =   new   system.drawing.size(62,   28);  
  this.button1.tabindex   =   5;  
  this.button1.text   =   "exit";  
  this.button1.click   +=   new   system.eventhandler(this.button1_click);  
  //    
  //   timer1  
  //    
  this.timer1.enabled   =   true;  
  this.timer1.tick   +=   new   system.eventhandler(this.timer1_tick);  
  //    
  //   button2  
  //    
  this.button2.location   =   new   system.drawing.point(304,   144);  
  this.button2.name   =   "button2";  
  this.button2.size   =   new   system.drawing.size(128,   32);  
  this.button2.tabindex   =   6;  
  this.button2.text   =   "button2";  
  this.button2.click   +=   new   system.eventhandler(this.button2_click);  
  //    
  //   form1  
  //    
  this.autoscalebasesize   =   new   system.drawing.size(6,   14);  
  this.clientsize   =   new   system.drawing.size(512,   200);  
  this.controls.addrange(new   system.windows.forms.control[]   {  
      this.button2,  
      this.button1,  
      this.idwindowlabel,  
      this.captionwindowlabel,  
      this.label3,  
      this.label2,  
      this.label1});  
  this.name   =   "form1";  
  this.startposition   =   system.windows.forms.formstartposition.centerscreen;  
  this.text   =   "window   information";  
  this.most   =   true;  
  this.resumelayout(false);  
   
  }  
  #endregion  
   
  ///   <summary>  
  ///   the   main   entry   point   for   the   application.  
  ///   </summary>  
  [stathread]  
  static   void   main()    
  {  
  application.run(new   form1());  
  }  
   
  private   void   timer1_tick(object   sender,   system.eventargs   e)  
  {  
  //getactivewindow();  
  }  
   
  private   void   button1_click(object   sender,   system.eventargs   e)  
  {  
  this.close();  
  }  
   
  private   void   button2_click(object   sender,   system.eventargs   e)  
  {  
  getactivewindow();  
  }  
  }  
  }