IRunningObjectTable.Register

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lgs.lgs - 27 Jul 2006 01:19 GMT

Could someone take a look at the docs for this method?

http://windowssdk.msdn.microsoft.com/en-us/library/system.runtime.interopservice
s.comtypes.irunningobjecttable.register.aspx

In particular, I'm interested in the return value. The docs say it is an
HRESULT. However, I sincerely doubt this. If I'm not mistaken, what it is
actually returning is the cookie needed to do the
IRunningObjectTable.Revoke.

When you think about it, if there were an error, wouldn't you expect an
exception rather than an HRESULT?

However, I'm not 100% certain, and a double-check would be appreciated.

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Dmytro Lapshyn [MVP] - 27 Jul 2006 10:30 GMT

Hi,

It's a COM trick :) A _physical_ return value of the Register method *is* an
HRESULT. Here's the raw definition:

HRESULT Register(DWORD grfFlags, IUnknown * punkObject, IMoniker *
pmkObjectName, DWORD * pdwRegister);

As you can see, the cookie is physically the last output parameter.

However, in the .NET world, the Interop layer makes things simplier for you.
It hides the HRESULT and pretends that the cookie is *the* return value.
Should the returned HRESULT indicate failure, the Interop layer throws an
exception that, in particular, contains the actual HRESULT value.

Still with me? :) Feel free to follow up, I know it's not a straightforward
topic.

Signature

Regards,
Dmytro Lapshyn [MVP]
http://blogs.vbcity.com/DmytroL

> Could someone take a look at the docs for this method?
>
[quoted text clipped - 10 lines]
>
> However, I'm not 100% certain, and a double-check would be appreciated.

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lgs.lgs - 27 Jul 2006 21:30 GMT

> It's a COM trick :)

Thanks for the response.

Yes, I am familiar with the [PreserveSig] trick. And in general, this is a
good thing in .NET. However, since IRunningObjectTable is compiled code, I
can't change its behavior. So, this tells me that it will NOT, under any
circumstances, return an HRESULT to my c# code.

However, the docs which describe using this method specifically say that the
return value *is* an HRESULT. And they *don't* make any reference at all to
a cookie (which is essential to using ROT).

In short then, the docs are simply wrong. Which is what I suspected.

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IRunningObjectTable.Register

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