利用SendMessage实现C#进程间通信

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

使用内存映射文件

通过共享内存DLL共享内存

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.（ZT）
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.

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 WinFormSendMsg

{

public class Form1 : System.Windows.Forms.Form

{

private System.Windows.Forms.TextBox textBox1;

private System.Windows.Forms.Button button1;

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 );

}

private void InitializeComponent()

{

this.textBox1 = new System.Windows.Forms.TextBox();

this.button1 = new System.Windows.Forms.Button();

this.SuspendLayout();

//

// textBox1

//

this.textBox1.Location = new System.Drawing.Point(184, 24);

this.textBox1.Name = "textBox1";

this.textBox1.Size = new System.Drawing.Size(128, 21);

this.textBox1.TabIndex = 0;

this.textBox1.Text = "textBox1";

//

// button1

//

this.button1.Location = new System.Drawing.Point(344, 16);

this.button1.Name = "button1";

this.button1.Size = new System.Drawing.Size(112, 32);

this.button1.TabIndex = 1;

this.button1.Text = "button1";

this.button1.Click += new System.EventHandler(this.button1_Click);

//

// Form1

//

this.AutoScaleBaseSize = new System.Drawing.Size(6, 14);

this.ClientSize = new System.Drawing.Size(536, 142);

this.Controls.AddRange(new System.Windows.Forms.Control[] {

this.button1,

this.textBox1});

this.Name = "Form1";

this.Text = "发送方窗体";

this.ResumeLayout(false);

}

static void Main()

{

Application.Run(new Form1());

}

[DllImport("User32.dll",EntryPoint="SendMessage")]

private static extern int SendMessage(

int hWnd, // handle to destination window

int Msg, // message

int wParam, // first message parameter

ref COPYDATASTRUCT lParam // second message parameter

);

[DllImport("User32.dll",EntryPoint="FindWindow")]

private static extern int FindWindow(string lpClassName,string

lpWindowName);

private void button1_Click(object sender, System.EventArgs e)

{

int WINDOW_HANDLER = FindWindow(null,@"接收方窗体");

if(WINDOW_HANDLER == 0)

{

}

else

{

byte[] sarr = System.Text.Encoding.Default.GetBytes(this.textBox1.Text);

int len = sarr.Length;

COPYDATASTRUCT cds;

cds.dwData = (IntPtr) 100;

cds.lpData = this.textBox1.Text;

cds.cbData = len + 1;

SendMessage(WINDOW_HANDLER, WM_COPYDATA, 0, ref cds);

}

}

}

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 );

}

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 = "接收方窗体";

this.ResumeLayout(false);

}

static void Main()

{

Application.Run(new Form1());

}

protected override void DefWndProc(ref System.Windows.Forms.Message m)

{

switch(m.Msg)

{

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;

}

}

}

public struct COPYDATASTRUCT

{

public IntPtr dwData;

public int cbData;

[MarshalAs(UnmanagedType.LPStr)] public string lpData;

}

}