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

[John Doe]

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

public ref class TestClass
{
public:
event System::EventHa ndler^ 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(so meEventHandler) ;

[Peter Duniho]

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

On Thu, 31 Jul 2008 13:48:14 -0700, John Doe <john@doe.comwr ote:

I have a C++/CLI assembly that exposes an event, e.g:
>
public ref class TestClass
{
public:
event System::EventHa ndler^ 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(so meEventHandler) ;

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

[John Doe]

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

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 TestManagedCLIE vents
{
class Program
{
static void Main(string[] args)
{
Class1 testclass = new Class1();
testclass.someE vent = new EventHandler(so meEventHandler) ;
}

private void someEventHandle r(Object ojb, EventArgs args)
{

}
}
}

The compilation error is: ManagedEvents.C lass1 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" <NpOeStPeAdM@nn owslpianmk.comw rote in message
news:op.ue6dy0a 48jd0ej@petes-computer.local. ..

>
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
>

[Peter Duniho]

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

On Thu, 31 Jul 2008 14:47:33 -0700, John Doe <john@doe.comwr ote:

Here's more info:
>
// ManagedEvents.h
#pragma once
using namespace System;
namespace ManagedEvents {
>
public ref class Class1
{
event EventHandler^ someEvent;
};
}

Shouldn't that be:

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

???

Your original post included the "public:", but the above does not. If you
forgot that, well...that would certainly explain the error. :)

Pete

[John Doe]

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

Nevermind, i noticed i didn't declare the event as public...


"John Doe" <john@doe.comwr ote in message
news:%23KXjNc18 IHA.356@TK2MSFT NGP02.phx.gbl.. .

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 TestManagedCLIE vents
{
class Program
{
static void Main(string[] args)
{
Class1 testclass = new Class1();
testclass.someE vent = new EventHandler(so meEventHandler) ;
}
>
private void someEventHandle r(Object ojb, EventArgs args)
{
>
}
}
}
>
The compilation error is: ManagedEvents.C lass1 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" <NpOeStPeAdM@nn owslpianmk.comw rote in message
news:op.ue6dy0a 48jd0ej@petes-computer.local. ..

>>
>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
>>

>

[Jon Skeet [C# MVP]]

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

John Doe <john@doe.comwr ote:

<snip>

The compilation error is: ManagedEvents.C lass1 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.

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

testclass.someE vent += new EventHandler(so meEventHandler) ;

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.

--
Jon Skeet - <skeet@pobox.co m>
Web site: http://www.pobox.com/~skeet
Blog: http://www.msmvps.com/jon.skeet
C# in Depth: http://csharpindepth.com