>Hi,
> Is it OK to have messagebox in COM/DCOM object? If so, will the messagebox prompted on client's screen or on server client?
>

In an in-process (.DLL) server, no, you can't. On an out-of-process server, you can have it but it does not become a part of the client UI; if you're using a COM object instantiated remotely, it appears on the server not on the client, instantiated locally, it'll have it's own window context.