C# Signature:

[DllImport("user32.dll", SetLastError=true)]
static extern bool GetWindowRect(IntPtr hwnd, out RECT lpRect);

VB.NET Signature:

<DllImport("user32.dll")> _
Private Shared Function GetWindowRect(ByVal hWnd As HandleRef, ByRef lpRect As RECT) As Boolean
End Function

User-Defined Types:

RECT

Notes:

The Win32 RECT is not binary compatible with System.Drawing.Rectangle.

Tips & Tricks:

Please note that this does NOT work properly with Windows Vista Aero (this includes Windows 10), and reports faulty values. This is largely due to Aero incorporating additional invisible borders which are used to "resize" the window using the cursor. In this instance, the developer should look into using DwmGetWindowAttribute (dwmapi.dll) with DWMWA_EXTENDED_FRAME_BOUNDS.

For .NET CF you may need to replace user32.dll with coredll.dll

Please add some!

Sample Code:

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool GetWindowRect(HandleRef hWnd, out RECT lpRect);

[StructLayout(LayoutKind.Sequential)]
public struct RECT
{
     public int Left;        // x position of upper-left corner
     public int Top;         // y position of upper-left corner
     public int Right;       // x position of lower-right corner
     public int Bottom;      // y position of lower-right corner
}

Rectangle myRect = new Rectangle();

private void button1_Click(object sender, System.EventArgs e)
{
     RECT rct;

     if(!GetWindowRect(new HandleRef(this, this.Handle), out rct ))
     {
     MessageBox.Show("ERROR");
             return;
     }
     MessageBox.Show( rct.ToString() );

     myRect.X = rct.Left;
     myRect.Y = rct.Top;
     myRect.Width = rct.Right - rct.Left + 1;
     myRect.Height = rct.Bottom - rct.Top + 1;
}

Alternative Managed API: