.NET: how to PInvoke UpdateProcThreadAttribute

Question

I'm trying PInvoke UpdateProcThreadAttribute()on Windows 7, but my attempts just keep returning FALSE with the latest Win32 error equal to 50.

Function declaration (from MSDN)

BOOL WINAPI UpdateProcThreadAttribute(
  __inout    LPPROC_THREAD_ATTRIBUTE_LIST lpAttributeList,
  __in       DWORD dwFlags,
  __in       DWORD_PTR Attribute,
  __in       PVOID lpValue,
  __in       SIZE_T cbSize,
  __out_opt  PVOID lpPreviousValue,
  __in_opt   PSIZE_T lpReturnSize
);

Here is my attempt to sign PInvoke:

[DllImport("kernel32.dll", CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool UpdateProcThreadAttribute
(
            IntPtr lpAttributeList,
            UInt32 dwFlags,
            ref UInt32 Attribute,
            ref IntPtr lpValue,
            ref IntPtr cbSize,
            IntPtr lpPreviousValue,
            IntPtr lpReturnSize
);

Is this expression reasonable? Thanks.

Answer 1

You have a few problems with the declaration, but one that gives you an unsupported error is an attribute parameter. DWORD_PTR is not a pointer, but rather an unsigned integer, not a ref uint, it should be IntPtr.

The declaration I would use is as follows:

    [DllImport("kernel32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool UpdateProcThreadAttribute(
        IntPtr lpAttributeList, uint dwFlags, IntPtr Attribute,
        IntPtr lpValue, IntPtr cbSize, IntPtr lpPreviousValue, 
        IntPtr lpReturnSize);

EDIT:

I tried to do this as a comment, but it is not very well coded.

IntPtr . - :

IntPtr hProcess //previously retrieved.
IntPtr lpAttributeList //previously allocated using InitializeProcThreadAttributeList and Marshal.AllocHGlobal.

const int PROC_THREAD_ATTRIBUTE_PARENT_PROCESS = 0x00020000;
IntPtr lpValue = Marshal.AllocHGlobal(IntPtr.Size); 
Marshal.WriteIntPtr(lpValue, hProcess);
if(UpdateProcThreadAttribute(lpAttributeList, 0, (IntPtr)PROC_THREAD_ATTRIBUTE_PARENT_PROCESS, lpValue, (IntPtr)IntPtr.Size, IntPtr.Zero, IntPtr.Zero))
{
    //do something
}

//Free lpValue only after the lpAttributeList is deleted.