C# Definition:

[StructLayout(LayoutKind.Sequential)
public struct FILTER_MESSAGE_HEADER {
   public UInt32 ReplyLength;
   public UInt64 MessageId;
}

VB Definition:

Structure FILTER_MESSAGE_HEADER
   Public TODO
End Structure

User-Defined Field Types:

None.

Notes:

To receive messages from a kernel-mode minifilter, a user-mode application typically defines a custom message structure. This structure typically consists of this header structure, followed by an application-defined structure to hold the actual message data.