c# browser kordinata tıklatma

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace WindowsFormsApplication_22979038
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void MainForm_Load(object sender, EventArgs e)
        {
            this.webBrowser.DocumentText = "<a id='goLink' href='javascript:alert(\"Hello!\"),undefined'>Go</a><script></script>";

            this.webBrowser.DocumentCompleted += webBrowser_DocumentCompleted;
        }

        void webBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            var element = this.webBrowser.Document.GetElementById("goLink");
            element.Focus();
            var hwnd = GetFocus();
            if (!IsChild(this.webBrowser.Handle, hwnd))
                throw new ApplicationException("Unexpected focused window.");

            var rect = GetElementRect(element);
            IntPtr wParam = (IntPtr)MK_LBUTTON;
            IntPtr lParam = (IntPtr)(rect.Left | rect.Top << 16);
            PostMessage(hwnd, WM_LBUTTONDOWN, wParam, lParam);
            PostMessage(hwnd, WM_LBUTTONUP, wParam, lParam);
        }

        // get the element rect in window client area coordinates
        static Rectangle GetElementRect(HtmlElement element)
        {
            var rect = element.OffsetRectangle;
            int left = 0, top = 0;
            var parent = element;
            while (true)
            {
                parent = parent.OffsetParent;
                if (parent == null)
                    return new Rectangle(rect.X + left, rect.Y + top, rect.Width, rect.Height);
                var parentRect = parent.OffsetRectangle;
                left += parentRect.Left;
                top += parentRect.Top;
            }
        }

        // interop

        const int MK_LBUTTON = 0x0001;
        const int WM_LBUTTONDOWN = 0x0201;
        const int WM_LBUTTONUP = 0x0202;

        [StructLayout(LayoutKind.Sequential)]
        public struct POINT
        {
            public int x;
            public int y;
        }

        [DllImport("User32.dll", CharSet = CharSet.Auto)]
        static extern int PostMessage(IntPtr hwnd, int msg, IntPtr wparam, IntPtr lparam);

        [DllImport("User32.dll", ExactSpelling = true, CharSet = CharSet.Auto)]
        static extern IntPtr GetFocus();

        [DllImport("User32.dll", SetLastError = true, ExactSpelling = true, CharSet = CharSet.Auto)]
        static extern bool IsChild(IntPtr hWndParent, IntPtr hWnd);
    }
}