Marshal.AllocHGlobal VS Marshal.AllocCoTaskMem, Marshal.SizeOf VS sizeof()

Question

I have the following struct:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
public struct WAVEHDR
{
    internal IntPtr lpData;   // pointer t         


        

Answer 1

1) Marshal.AllocHGlobal will work for sure. Based on the docs for Marshal.AllocCoTaskMem, Marshal.AllocCoTaskMem should work too.

2) Use Marshal.SizeOf(typeof(WAVEHDR)). Although you can use the Marshal.SizeOf method, the value returned by this method is not always the same as the value returned by sizeof. Marshal.SizeOf returns the size after the type has been marshaled, whereas sizeof returns the size as it has been allocated by the common language runtime, including any padding.