    [Serializable, StructLayout(LayoutKind.Sequential)]
    public struct RECT {
      public int Left;
      public int Top;
      public int Right;
      public int Bottom;

      public RECT(int left_, int top_, int right_, int bottom_) {
        Left = left_;
        Top = top_;
        Right = right_;
        Bottom = bottom_;
      }

      public int Height { get { return Bottom - Top; } }
      public int Width { get { return Right - Left; } }
      public Size Size { get { return new Size(Width, Height); } }

      public Point Location { get { return new Point(Left, Top); } }

      // Handy method for converting to a System.Drawing.Rectangle
      public Rectangle ToRectangle()
        { return Rectangle.FromLTRB(Left, Top, Right, Bottom); }

      public static RECT FromRectangle(Rectangle rectangle) {
        return new RECT(rectangle.Left, rectangle.Top, rectangle.Right, rectangle.Bottom);
      }

      public override int GetHashCode() {
        return Left ^ ((Top << 13) | (Top >> 0x13))
          ^ ((Width << 0x1a) | (Width >> 6))
          ^ ((Height << 7) | (Height >> 0x19));
      }
    }

VB .NET Signature:

<StructLayout(LayoutKind.Sequential)> _
Public Structure RECT
   Public Left As Integer
   Public Top As Integer
   Public Right As Integer
   Public Bottom As Integer
End Structure

Public Shared Function ToRectangle(ByVal sourceRect As RECT) As Rectangle
   Return New Rectangle(sourceRect.Left, sourceRect.Top, sourceRect.Right - sourceRect.Left, sourceRect.Bottom - sourceRect.Top)
End Function