How do I consume an event from C++/CLI in C#?

  • Thread starter Thread starter John Doe
  • Start date Start date
J

John Doe

I have a C++/CLI assembly that exposes an event, e.g:

public ref class TestClass
{
public:
event System::EventHandler^ someEvent;
}

My main C# project references this C++/CLI assembly, and I can see the
someEvent event in the Object Browser. However, when I tried to handle the
event, VS2008 complains that someEvent does not exist. Why is this so,
perhaps I did it wrong?

TestClass obj = new TestClass();
obj.someEvent += new EventHandler(someEventHandler);
 
Here's more info:

// ManagedEvents.h
#pragma once
using namespace System;
namespace ManagedEvents {

public ref class Class1
{
event EventHandler^ someEvent;
};
}

Here's the main C# code that tries to handle someEvent:

using System;
using ManagedEvents;

namespace TestManagedCLIEvents
{
class Program
{
static void Main(string[] args)
{
Class1 testclass = new Class1();
testclass.someEvent = new EventHandler(someEventHandler);
}

private void someEventHandler(Object ojb, EventArgs args)
{

}
}
}

The compilation error is: ManagedEvents.Class1 does not contain a definition
for 'someEvent' and no extension method 'someEvent' accepting a first
argument of type 'ManagedEvents.Class1' could be found (are you missing a
using directive or an assembly reference?)

I've made sure the ManagedEvents C++/CLI assembly is referenced from the C#
project.
 
Nevermind, i noticed i didn't declare the event as public...


John Doe said:
Here's more info:

// ManagedEvents.h
#pragma once
using namespace System;
namespace ManagedEvents {

public ref class Class1
{
event EventHandler^ someEvent;
};
}

Here's the main C# code that tries to handle someEvent:

using System;
using ManagedEvents;

namespace TestManagedCLIEvents
{
class Program
{
static void Main(string[] args)
{
Class1 testclass = new Class1();
testclass.someEvent = new EventHandler(someEventHandler);
}

private void someEventHandler(Object ojb, EventArgs args)
{

}
}
}

The compilation error is: ManagedEvents.Class1 does not contain a
definition for 'someEvent' and no extension method 'someEvent' accepting a
first argument of type 'ManagedEvents.Class1' could be found (are you
missing a using directive or an assembly reference?)

I've made sure the ManagedEvents C++/CLI assembly is referenced from the
C# project.

Peter Duniho said:
Do you have a concise-but-complete code sample that demonstrates the
error? What is the _exact_ text of the error? Do you have the C++/CLI
assembly properly referenced and included in a "using" directive in your
C# project?

What you posted looks fine. So it seems to me the problem must be in
some of the information you left out of your question.

Pete
Click to expand...
Click to expand...
 
The compilation error is: ManagedEvents.Class1 does not contain a definition
for 'someEvent' and no extension method 'someEvent' accepting a first
argument of type 'ManagedEvents.Class1' could be found (are you missing a
using directive or an assembly reference?)

I've made sure the ManagedEvents C++/CLI assembly is referenced from the C#
project.
Click to expand...

Well, apart from anything else you shouldn't be trying to *assign* to
the event - you should be trying to *subscribe to it:

testclass.someEvent += new EventHandler(someEventHandler);

However, if that were the only problem I'd expect a different error
message.

After a bit of experimenting, it seems that the problem is just that
the event isn't public. Make it public, change the code as above, and
it should be okay.
 
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