如何在C#用WM_COPYDATA消息来实现两个进程之间传递数据

http://www.cnblogs.com/cdo/archive/2005/06/08/170457.html

 

简介:

本文着重讲述了如果用WM_COPYDATA消息来实现两个进程之间传递数据。

进程之间通讯的几种方法:

在Windows程序中，各个进程之间常常需要交换数据，进行数据通讯。常用的方法有

1、使用内存映射文件
2、通过共享内存DLL共享内存
3、使用SendMessage向另一进程发送WM_COPYDATA消息

比起前两种的复杂实现来，WM_COPYDATA消息无疑是一种经济实惠的一中方法。

WM_COPYDATA消息的主要目的是允许在进程间传递只读数据。Windows在通过WM_COPYDATA消息传递期间，不提供继承同步方式。SDK文档推荐用户使用SendMessage函数，接受方在数据拷贝完成前不返回，这样发送方就不可能删除和修改数据。

这个函数的原型及其要用到的结构如下:

SendMessage(hwnd,WM_COPYDATA,wParam,lParam);
其中,WM_COPYDATA对应的十六进制数为0x004A

wParam设置为包含数据的窗口的句柄。lParam指向一个COPYDATASTRUCT的结构：
typedef struct tagCOPYDATASTRUCT{ DWORD dwData;//用户定义数据 DWORD cbData;//数据大小 PVOID lpData;//指向数据的指针 }COPYDATASTRUCT;
该结构用来定义用户数据。

具体过程如下:
首先，在发送方，用FindWindow找到接受方的句柄，然后向接受方发送WM_COPYDATA消息。

接受方在DefWndProc事件中，来处理这条消息。由于中文编码是两个字节，所以传递中文时候字节长度要搞清楚。

代码中有适量的解释，大家请自己看吧。

具体代码如下:
//--------------------------------------------------- //发送方: //--------------------------------------------------- using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; using System.Runtime.InteropServices; namespace WindowsFormGetMsg { public class Form1 : System.Windows.Forms.Form { private System.Windows.Forms.TextBox textBox1; private System.ComponentModel.Container components = null; const int WM_COPYDATA = 0x004A; public Form1() { InitializeComponent(); } protected override void Dispose(bool disposing) { if (disposing) { if (components != null) { components.Dispose(); } } base.Dispose(disposing); } #region Windows Form Designer generated code private void InitializeComponent() { this.textBox1 = new System.Windows.Forms.TextBox(); this.SuspendLayout(); // // textBox1 // this.textBox1.Location = new System.Drawing.Point(176, 32); this.textBox1.Name = "textBox1"; this.textBox1.Size = new System.Drawing.Size(160, 21); this.textBox1.TabIndex = 0; this.textBox1.Text = "textBox1"; // // Form1 // this.AutoScaleBaseSize = new System.Drawing.Size(6, 14); this.ClientSize = new System.Drawing.Size(432, 266); this.Controls.AddRange(new System.Windows.Forms.Control[] { this.textBox1 }); this.Name = "Form1"; this.Text = "接收方"; this.ResumeLayout(false); } #endregion [STAThread] static void Main() { Application.Run(new Form1()); } protected override void DefWndProc(ref System.Windows.Forms.Message m) { switch (m.Msg) { //接收自定义消息 USER，并显示其参数 case WM_COPYDATA: COPYDATASTRUCT mystr = new COPYDATASTRUCT(); Type mytype = mystr.GetType(); mystr = (COPYDATASTRUCT)m.GetLParam(mytype); this.textBox1.Text = mystr.lpData; break; default: base.DefWndProc(ref m); break; } } } [StructLayout(LayoutKind.Sequential)] public struct COPYDATASTRUCT { public IntPtr dwData; public int cbData; [MarshalAs(UnmanagedType.LPStr)] public string lpData; } } //--------------------------------------------------- //接受方 //--------------------------------------------------- using System; using System.Drawing; using System.Collections; using System.ComponentModel; using System.Windows.Forms; using System.Data; using System.Runtime.InteropServices; namespace WindowsFormGetMsg { public class Form1 : System.Windows.Forms.Form { private System.Windows.Forms.TextBox textBox1; private System.ComponentModel.Container components = null; const int WM_COPYDATA = 0x004A; public Form1() { InitializeComponent(); } protected override void Dispose(bool disposing) { if (disposing) { if (components != null) { components.Dispose(); } } base.Dispose(disposing); } #region Windows Form Designer generated code private void InitializeComponent() { this.textBox1 = new System.Windows.Forms.TextBox(); this.SuspendLayout(); // // textBox1 // this.textBox1.Location = new System.Drawing.Point(176, 32); this.textBox1.Name = "textBox1"; this.textBox1.Size = new System.Drawing.Size(160, 21); this.textBox1.TabIndex = 0; this.textBox1.Text = "textBox1"; // // Form1 // this.AutoScaleBaseSize = new System.Drawing.Size(6, 14); this.ClientSize = new System.Drawing.Size(432, 266); this.Controls.AddRange(new System.Windows.Forms.Control[] { this.textBox1 }); this.Name = "Form1"; this.Text = "接收方"; this.ResumeLayout(false); } #endregion [STAThread] static void Main() { Application.Run(new Form1()); } protected override void DefWndProc(ref System.Windows.Forms.Message m) { switch (m.Msg) { //接收自定义消息 USER，并显示其参数 case WM_COPYDATA: COPYDATASTRUCT mystr = new COPYDATASTRUCT(); Type mytype = mystr.GetType(); mystr = (COPYDATASTRUCT)m.GetLParam(mytype); this.textBox1.Text = mystr.lpData; break; default: base.DefWndProc(ref m); break; } } } [StructLayout(LayoutKind.Sequential)] public struct COPYDATASTRUCT { public IntPtr dwData; public int cbData; [MarshalAs(UnmanagedType.LPStr)] public string lpData; } }