C# Definition:

struct GUID {
   public TODO;
}

VB Definition:

<StructLayout(LayoutKind.Sequential)> _
Private Structure GUID
   Dim a As Integer
   Dim b As Short
   Dim c As Short
   <MarshalAs(UnmanagedType.ByValArray, SizeConst:=7)> _
   Dim d() As Byte
End Structure

User-Defined Field Types:

None.

Notes:

You should use System.Guid instead.