Picking up HRESULT returned from C++ COM inC# .NET code

Question

0.00/5 (No votes)

See more:

I'm calling a COM written in C++ from a .NET code written in C#.

The COM interface methods return HRESULT to indicate whether the call was successful.
However, when I look at the interface methods in C#, they claim to be void functions.

How do I pick up the HRESULTs from the COM then?

STDMETHOIMP CMyCOMObject::XMyCOMInterface::MyMethod()
{
	METHOD_PROLOGUE(CMyCOMObject, MyCOMInterface);
	return S_OK;
}

void Foo()
{
	MyCOM.IMyCOMInterface m_myCOM = new MyCOM.IMyCOMInterface;
	int nOut = m_myCOM.MyMethod(); // ERROR! C# thinks MyMethod is a void function!
}

Posted 22-Jan-13 20:04pm

PaulowniaK

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Maxim Kartavenkov · Accepted Answer · 2013-01-22T20:28:00

Hello,

By default COM wrapped as void on output, but it throws an exception if your method returns failed HRESULT.
You can handle COMException[^] in catch block. The COMException.HResult is the error code.

Another way is to create your own wrapper and specify PreserveSig[^] Attribute for the method and makes returns int instead of void.

More information about specified HRESULTS and .NET exceptions:
How to: Map HRESULTs and Exceptions[^]

Regards,
Maxim.