如何在C#用WM_COPYDATA消息来实现两个进程之间传递数据

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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;
}
}