Hi all,
I'm trying to make a pinvoke call to a legacy c dll. One method has a
structure as input.
The managed structure looks like this:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public struct Info
{
    public Version cryptokiVersion;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
    public string manufacturerID;
    public uint flags;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
    public string libraryDescription;
    public Version libraryVersion;
}

the inner Version structure:
public struct Version
{
    public byte major;
    public byte minor;
}

I need this structure to have exactly 72 bytes, as this is the size of the c
counterpart. On the first look, it should have 72 bytes (2 bytes for Version
x 2 + 32 bytes for the two ansi strings x 2 + 4 bytes uint = 72).
Unfortunately, Marshal.SizeOf calculates the size of this structure as 76,
although SizeOf applied to the individual members returns the correct,
expected values...

If I remove the uint, the size from Marshal.SizeOf suddenly drops to 68,
which is equal to the manualy calculated one. A uint takes up 4 bytes though
(Marshal.SizeOf confirms this), so why did the size drop by 8 bytes, not 4?.

If I replace the uint with two shorts (which are equal in size to one uint),
the size from Marshal.SizeOf is now correctly 72 (68 + 2x2).
Is this a bug in the framework (2.0.50727), or am I doing something wrong?

Thanks in advance for any insights...