C#进程间通信--API传递参数(SendMessage）

我们不仅可以传递系统已经定义好的消息，还可以传递自定义的消息（只需要发送消息端和接收消息端对自定义的消息值统一即可）。下面的发送和接收端同时演示了系统消息和自定义的消息。消息统一采用4位16进制的数。

1.系统消息使用的是0x0100(WM_KEYDOWN)；0x0000--0x0400是系统自定义的消息，其中0x0000为WM_NULL,0x0400为WM_USER。0x0400以后的数值我们可以作为自定义的消息值。（见附录）

2.自定义消息Message，代码如下：

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3.接收端和发送端

接收端Form1：

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public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
[DllImport("User32.dll", EntryPoint = "SendMessage")]
private static extern int SendMessage(IntPtr hWnd, int msg, uint wParam, uint lParam);
//[DllImport("MessageDLL.dll", EntryPoint = "StartSendMessage")]//MessageDLL找不到
//private static extern int StartSendMessage(IntPtr hWnd);
//自己触发自定义消息
private void button1_Click(object sender, EventArgs e)
{
SendMessage(this.Handle, Message.WM_TEST, 100, 200);
}
private void button2_Click(object sender, EventArgs e)
{
//StartSendMessage(this.Handle);
}
//响应和处理自定义消息
protected override void DefWndProc(ref System.Windows.Forms.Message m)
{
string message;
switch (m.Msg)
{
case Message.WM_TEST://处理消息
message = string.Format("收到从应用程序发出的消息！参数为：{0}, {1}", m.WParam, m.LParam);
MessageBox.Show(message);
break;
//case Message.WM_MSG:
// message = string.Format("收到从DLL发出的消息！参数为：{0}, {1}", m.WParam, m.LParam);
// MessageBox.Show(message);
// break;
default:
base.DefWndProc(ref m);
break;
}
}
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
this.label1.Text = e.KeyValue.ToString();
}
}

发送端Form2：button1启动接收端，button2关闭接收端,button3传递系统消息和自定义的消息。

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public partial class Form1 : Form
{
[DllImport("User32.dll", EntryPoint = "SendMessage")]
private static extern int SendMessage(IntPtr hWnd, int msg, int wParam, int lParam);
//[DllImport("MessageDLL.dll", EntryPoint = "StartSendMessage")]//MessageDLL找不到
//private static extern int StartSendMessage(IntPtr hWnd);
//internal string local = "this is a local internal";
public Form1()
{
InitializeComponent();
}
//ClassLibrary1.Class1 cla = new ClassLibrary1.Class1();
ProcessStartInfo startInfo = new ProcessStartInfo();
Process pro = new Process();
private void Form1_Load(object sender, EventArgs e)
{
startInfo.FileName = @"F:\Projects\WindowsFormsApplication1\WindowsFormsApplication1\bin\Debug\WindowsFormsApplication1.exe";
pro.StartInfo = startInfo;
}
private void button1_Click(object sender, EventArgs e)
{
pro.Start();
}
private void button2_Click(object sender, EventArgs e)
{
pro.Kill();
}
private void button3_Click(object sender, EventArgs e)
{
IntPtr hWnd = pro.MainWindowHandle;
int data = Convert.ToInt32(this.textBox1.Text);
SendMessage(hWnd, 0x0100, data, 0);
SendMessage(hWnd, Message.WM_TEST, 300, 300);
}