Error on execution of a method (.NET / COM)

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I have one Initialize() in my class and I am calling a delegate wrapper method from this function as follows (the call back method will call around 20 times in a sec),

C#

public Initialize()
{
                CX_OUTPUT_CALLBACK cb = new CX_OUTPUT_CALLBACK(OutDelegateCb);
                AureusSDK_Wrapper_VideoCallbackFunSetup.CX_SetOuputCallBack(cb, cnt);
}

public static void OutDelegateCb(IntPtr p_aureus_video_output, int num_of_people, IntPtr pObject)
{
 //Process the video...
}

I am getting the below error, when I execute the method. Could you anyone help me to resolve this issue:

A callback was made on a garbage collected delegate of type 'FaceTracker_Abc!AAA.VideoAnalytics.Framework.Implementations.FaceTracker_Abc.CX_OUTPUT_CALLBACK::Invoke'. This may cause application crashes, corruption and data loss. When passing delegates to unmanaged code, they must be kept alive by the managed application until it is guaranteed that they will never be called.

Posted 27-Jun-13 0:28am

Jeneesh K. Velayudhan

Updated 27-Jun-13 1:19am

Leo Chapiro

v2

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2 solutions

Solution 2

Thank you, Ron Beyer...

It worked...:)

Posted 28-Jun-13 0:44am

Jeneesh K. Velayudhan

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Ron Beyer · Accepted Answer · 2013-06-27T02:34:00

C#

public Initialize()
{
                CX_OUTPUT_CALLBACK cb = new CX_OUTPUT_CALLBACK(OutDelegateCb);
                AureusSDK_Wrapper_VideoCallbackFunSetup.CX_SetOuputCallBack(cb, cnt);
                GC.KeepAlive(cb);
}
 
public static void OutDelegateCb(IntPtr p_aureus_video_output, int num_of_people, IntPtr pObject)
{
 //Process the video...
}

That would prevent garbage collection from collecting your object. The problem is that you don't havea ny reference (outside of COM) to the "cb" variable. Since garbage collecting is a reference counting operation, when the garbage collector runs it sees the "cb" is not referenced anywhere and garbage collects it.