旅途

WM_COPYDATA消息的主要目的是允許在進程間傳遞只讀數據。Windows在通過WM_COPYDATA消息傳遞期間，不提供繼承同步方式。SDK文檔推薦用戶使用SendMessage函數，接受方在數據拷貝完成前不返回，這樣發(fā)送方就不可能刪除和修改數據：
這個函數的原型及其要用到的結構如下:
SendMessage(hwnd,WM_COPYDATA,wParam,lParam);
其中,WM_COPYDATA對應的十六進制數為0x004A
wParam設置為包含數據的窗口的句柄。lParam指向一個COPYDATASTRUCT的結構：
typedef struct tagCOPYDATASTRUCT{
DWORD dwData;//用戶定義數據
DWORD cbData;//數據大小
PVOID lpData;//指向數據的指針
}COPYDATASTRUCT;
該結構用來定義用戶數據。
具體過程如下:

首先,在發(fā)送方,用FindWindow找到接受方的句柄,然后向接受方發(fā)送WM_COPYDATA消息.
接受方在DefWndProc事件中,來處理這條消息.由于中文編碼是兩個字節(jié),所以傳遞中文時候字節(jié)長度要搞清楚.
體代碼如下:
//---------------------------------------------------
//發(fā)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 = "發(fā)送方窗體";
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,@"接收方窗體");
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 = "接收方窗體";
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;
}
}