c simulates mouse clicks with SendMessage in WebBrowser

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Text; 
using System.Windows.Forms; 
using System.Runtime.InteropServices; 

namespace BrowserMouseClick 
{ 
public partial class Form1 : Form 
{ 
     [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)] 
     static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam); 

     [DllImport("user32.dll", SetLastError = true)] 
     static extern IntPtr GetWindow(IntPtr hWnd, uint uCmd); 

     [DllImport("user32.dll", CharSet = CharSet.Auto)] 
     static extern int GetClassName(IntPtr hWnd, StringBuilder lpClassName, int nMaxCount); 

     public Form1() 
     { 
         InitializeComponent(); 
     } 

     private void Form1_Load(object sender, EventArgs e) 
     { 
         webBrowser1.Navigate("http://www.devpub.com"); 
     } 

     private void btnMouseClick_Click(object sender, EventArgs e) 
     { 
         int x = 100; // X coordinate of the click 
         int y = 80; // Y coordinate of the click 
         IntPtr handle = webBrowser1.Handle; 
         StringBuilder className = new StringBuilder(100); 
         while (className.ToString() != "Internet Explorer_Server") // The class control for the browser 
         { 
             handle = GetWindow(handle, 5); // Get a handle to the child window 
             GetClassName(handle, className, className.Capacity); 
         } 

         IntPtr lParam = (IntPtr)((y << 16) | x); // The coordinates 
         IntPtr wParam = IntPtr.Zero; // Additional parameters for the click (e.g. Ctrl) 
         const uint downCode = 0x201; // Left click down code 
         const uint upCode = 0x202; // Left click up code 
         SendMessage(handle, downCode, wParam, lParam); // Mouse button down 
         SendMessage(handle, upCode, wParam, lParam); // Mouse button up 
     } 
} 
}

Want to simulate the mouse click in WebBrowser control, on baidu for a long time, how also can't find, or google powerful, found in a foreign website, the code is more clear, do not explain.