簡介:
本文着重講述瞭如果用WM_COPYDATA消息來實現兩個進程之間傳遞數據.
進程之間通訊的幾種方法:
在Windows程序中，各個進程之間常常需要交換數據，進行數據通訊。常用的方法有
使用內存映射文件
通過共享內存DLL共享內存
使用SendMessage向另一進程發送WM_COPYDATA消息
比起前兩種的複雜實現來,WM_COPYDATA消息無疑是一種經濟實惠的一中方法.
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對應的十六進制數爲0×004A
wParam設置爲包含數據的窗口的句柄。lParam指向一個COPYDATASTRUCT的結構：typedef struct tagCOPYDATASTRUCT{該結構用來定義用戶數據。
DWORD dwData;//用戶定義數據
DWORD cbData;//數據大小
PVOID lpData;//指向數據的指針
}COPYDATASTRUCT;
具體過程如下:
首先,在發送方,用FindWindow找到接受方的句柄,然後向接受方發送WM_COPYDATA消息.
接受方在DefWndProc事件中,來處理這條消息.由於中文編碼是兩個字節,所以傳遞中文時候字節長度要搞清楚.
代碼中有適量的解釋,大家請自己看吧.
具體代碼如下://---------------------------------------------------
//發送方:
//---------------------------------------------------
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Data.OracleClient;
using System.Runtime.InteropServices;
namespace WinFormSendMsg
{
public partial class Form1 : System.Windows.Forms.Form
{
const int WM_COPYDATA = 0x004A;
public Form1()
{
InitializeComponent();
}
[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 cHENGDUBindingNavigatorSaveItem_Click(object sender, EventArgs e)
{
this.Validate();
this.cHENGDUBindingSource.EndEdit();
this.cHENGDUTableAdapter.Update(this.dataSet1.CHENGDU);
}
private void Form1_Load(object sender, EventArgs e)
{
// TODO: 這行代碼將數據加載到表“dataSet1.CHENGDU”中。您可以根據需要移動或移除它。
this.cHENGDUTableAdapter.Fill(this.dataSet1.CHENGDU);
}
private void cHENGDUDataGridView_CellClick(object sender, DataGridViewCellEventArgs e)
{
int WINDOW_HANDLER = FindWindow(null, @"接收方窗體");
if (WINDOW_HANDLER == 0)
{
MessageBox.Show("接收方未啓動");
}
else
{
byte[] sarr = System.Text.Encoding.Default.GetBytes(cHENGDUDataGridView.Rows[e.RowIndex].Cells[2].Value.ToString());
int len = sarr.Length;
COPYDATASTRUCT cds;
cds.dwData = (IntPtr)100;
cds.lpData = cHENGDUDataGridView.Rows[e.RowIndex].Cells[2].Value.ToString();
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 partial class Form1 : System.Windows.Forms.Form
{
const int WM_COPYDATA = 0x004A;
public Form1()
{
InitializeComponent();
}
[STAThread]
protected override void DefWndProc(ref System.Windows.Forms.Message m)
{
switch (m.Msg)
{
//接收自定義消息 USER，並顯示其參數
case WM_COPYDATA:
COPYDATASTRUCT mystr = new COPYDATASTRUCT();
Type mytype = mystr.GetType();
mystr = (COPYDATASTRUCT)m.GetLParam(mytype);
this.label1.Text = mystr.lpData;
break;
default:
base.DefWndProc(ref m);
break;
}
}
private void timer1_Tick(object sender, EventArgs e)
{
this.panel1.Location = new Point(panel1.Location.X, panel1.Location.Y - 1);
if ((panel1.Location.Y + panel1.Height) <= 0)
{
this.panel1.Location = new Point(panel1.Location.X, 310);
}
}
private void label1_TextChanged(object sender, EventArgs e)
{
this.panel1.Height = label1.Height;
this.panel1.Location = new Point(panel1.Location.X, 310);
}
}
[StructLayout(LayoutKind.Sequential)]
public struct COPYDATASTRUCT
{
public IntPtr dwData;
public int cbData;
[MarshalAs(UnmanagedType.LPStr)]
public string lpData;
}
}
