Marshalling riddle

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Joerg Krause - 14 Jul 2004 18:28 GMT

I've an interface with the following method:

void Show(
[In, MarshalAs(UnmanagedType.I4)]
int fShow);

void UIActivate(
[In, MarshalAs(UnmanagedType.I4)]
int fUIActivate);

When I call these methods, using this cocde in C#:

interopDocumentView.Show(-1);
interopDocumentView.UIActivate(-1);

I get the following error:

"Cannot marshal parameter #1: Invalid managed/unmanaged type
combination, (Int32/UInt32 must be combined with I4 or U4"

This is strange, as I marshal explicitly to I4 and -1 is obviously
Int32, as the error message stated.

Is there any thing I've forgotten in my interface definition??

Thanks for your thoughts,

Joerg

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RichM - 15 Jul 2004 21:47 GMT

Ive noticed that dotnet is really cumbersome when it comes to signed/unsigned integers. I always have trouble with interop when my operation moves a 1 into the sign bit of an int. For example, you can't assign an int to hex value 0xffffffff, even though you meant (-1) and it is perfectly mathematically correct to do so. So if you need to load a DWORD with a high and low word for a Platform SDK call, you really have to jump through some hoops. The same annoyance is caused by an int that is composed of bitflags.

> I've an interface with the following method:
>
[quoted text clipped - 24 lines]
>
> Joerg

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Marshalling riddle

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