ผมอยากปิดแท็บข้างๆ เมื่อใช้ IsMdicontainer เมื่อผมเอา Formไปติดตั้งข้างๆ ให้มันติด

using System.Runtime.InteropServices;
public const int WM_NCLBUTTONDOWN = 0xA1;
public const int HT_CAPTION = 0x2;

[DllImportAttribute("user32.dll")]
public static extern int SendMessage(IntPtr hWnd,  int Msg, int wParam, int lParam);
[DllImportAttribute("user32.dll")]
public static extern bool ReleaseCapture();
private void Form1_MouseDown(object sender, 
        System.Windows.Forms.MouseEventArgs e)
{     
    if (e.Button == MouseButtons.Left)
    {
        ReleaseCapture();
        SendMessage(Handle, WM_NCLBUTTONDOWN, HT_CAPTION, 0);
    }
}