C# sendmessage

以下是使用C#调用SendMessage函数的示例代码：

using System;
using System.Runtime.InteropServices;

class Program
{
    const int BM_CLICK = 0xF5;

    [DllImport("user32.dll", EntryPoint = "FindWindow")]
    private static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

    [DllImport("user32.dll", EntryPoint = "FindWindowEx")]
    private static extern IntPtr FindWindowEx(IntPtr hwndParent, IntPtr hwndChildAfter, string lpszClass, string lpszWindow);

    [DllImport("user32.dll", EntryPoint = "SendMessage")]
    private static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, int lParam);

    static void Main(string[] args)
    {
        IntPtr maindHwnd = FindWindow(null, "QQ用户登录");
        if (maindHwnd != IntPtr.Zero)
        {
            IntPtr childHwnd = FindWindowEx(maindHwnd, IntPtr.Zero, null, "登录");
            if (childHwnd != IntPtr.Zero)
            {
                SendMessage(childHwnd, BM_CLICK, 0, 0);
            }
            else
            {
                Console.WriteLine("没有找到子窗口");
            }
        }
        else
        {
            Console.WriteLine("没有找到窗口");
        }
    }
}

这段代码演示了如何使用C#调用SendMessage函数。首先，使用FindWindow函数找到QQ用户登录窗口的句柄，然后使用FindWindowEx函数找到登录按钮的句柄。最后，使用SendMessage函数发送BM_CLICK消息，模拟点击登录按钮。