using System.Runtime.InteropServices;
const uint TPM_LEFTBUTTON = 0;
const uint TPM_RIGHTBUTTON = 2;
const uint TPM_LEFTALIGN = 0;
const uint TPM_CENTERALIGN = 4;
const uint TPM_RIGHTALIGN = 8;
const uint TPM_TOPALIGN = 0;
const uint TPM_VCENTERALIGN = 0x10;
const uint TPM_BOTTOMALIGN = 0x20;
const uint TPM_RETURNCMD = 0x100;
const uint WM_SYSCOMMAND = 0x0112;
#region DllImport
[DllImport("User32.dll")]
static extern IntPtr GetSystemMenu(IntPtr hWnd, bool bRevert);
[DllImport("User32.dll")]
static extern bool GetCursorPos(out Point lpPoint);
[DllImport("User32.dll")]
static extern int TrackPopupMenu(IntPtr hMenu, uint uFlags,
int x, int y, int nReserved, IntPtr hWnd, out Rectangle prcRect);
[DllImport("User32.DLL")]
public static extern int SendMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);
#endregion
private void button1_Click(object sender, EventArgs e)
{
Point vPoint;
Rectangle vRect;
GetCursorPos(out vPoint);
SendMessage(Handle, WM_SYSCOMMAND, TrackPopupMenu(
GetSystemMenu(Handle, false),
TPM_RETURNCMD | TPM_LEFTBUTTON, vPoint.X, vPoint.Y,
0, Handle, out vRect), 0);
}