How to fire async events and c++/clr

  • Thread starter Thread starter Guest
  • Start date Start date
G

Guest

Greetings,

I am trying to fire aysnc events in c++/clr, and I can't seem to get it to
work.
It seems to work fine in c#, but when I try c++/clr, I can't seem to get it
to compile in the c++/clr class.

I.) Event Testing in C#, which works fine:
public class CSharpEventTest
{
public event CSharpDelegate AsyncEvent = null;
public event CSharpDelegate SyncEvent = null;

public void FireAsyncEvent(string message)
{
if (AsyncEvent == null) return;

AsyncEvent.BeginInvoke(message, null, this);
}

public void FireSyncEvent(string message)
{
if (SyncEvent == null) return;

SyncEvent(message);
}

}


II. Event Testing in MC++, which doesn't compile correctly.
public delegate bool MCDelegate(System::String^ errorCode);

public ref class MCEventTesting
{
public:
MCEventTesting(void);

event MCDelegate^ EventSync;
event MCDelegate^ EventASync;

public:
void FireEventAsync(System::String^ errorCode)
{
// Doesn't compile, gives an error:
//"invalid argument for delegate constructor; delegate target needs to be a
// pointer to a member function"
MyErrorDelegate^ delg = gcnew MyErrorDelegate(EventASync(errorCode));
delg.BeginInvoke(NULL, delg);
}

// Works fine
void FireEventSync(System::String^ errorCode)
{
EventSync(errorCode);
}
};

Thanks for any suggestions!
 
BartMan said:
public:
void FireEventAsync(System::String^ errorCode)
{
// Doesn't compile, gives an error:
//"invalid argument for delegate constructor; delegate target needs to be a
// pointer to a member function"
MyErrorDelegate^ delg = gcnew MyErrorDelegate(EventASync(errorCode));
Click to expand...

MyErrorDelegate^ delg = gcnew MyErrorDelegate(this,
&MCEventTesting::EventASync);

The first argument (this) is a handle to the handler class. The second
argument (&MCEventTesting::EventASync) is a pointer to the handler function.

Tom
 
Hello Tamas,

Thanks for the reply. I tried your recommendation for the method.
MyErrorDelegate^ delg = gcnew MyErrorDelegate(this,
&MCEventTesting::EventASync);
Click to expand...

But I get the following error:
Error 1 error C3364: invalid argument for delegate constructor; delegate
target needs to be a pointer to a member function

For some reason the "event MCDelegate^ EventASync;" is not working as a
member function.

Any ideas?
 
BartMan said:
But I get the following error:
Error 1 error C3364: invalid argument for delegate constructor; delegate
target needs to be a pointer to a member function
Click to expand...

You didn't disclose the declaration of MyErrorDelegate, but it looks
like it's not compatible with the handler. Your event handler must have
the exact same arguments and return type as the delegate. For example,
MCDelegate is declared

public delegate bool MCDelegate(System::String^ errorCode);

So the event handler must be declared

bool xxx(System::String^ errorCode);

Tom
 
You didn't disclose the declaration of MyErrorDelegate, but it looks
like it's not compatible with the handler. Your event handler must have
the exact same arguments and return type as the delegate. For example,
MCDelegate is declared
Click to expand...

Opps a typo on my part the delegate was declared, and the event is declared
below, and it has the same values, so I don't understand how it cannot
compile.
Especially since the c# works fine?

// Here is the Delegate:
public delegate bool MCDelegate(System::String^ errorCode);

public ref class MCEventTesting
{
public:
MCEventTesting(void);

event MCDelegate^ SyncEvent;
event MCDelegate^ AsyncEvent; // Async Event?????

public:
// Fire the event as an async event.
void fireErrorEventAsync(System::String^ errorCode)
{
// ERROR: "Complains that it must be a pointer to a member function."
MCDelegate^ delg = gcnew MCDelegate(this,&MCEventTesting::AsyncEvent);
AsyncEvent->BeginInvoke("test",nullptr,this);

// Also tried this, it didn't work complained that it needs to be a data
member.
// MCEventTesting::AsyncEvent->BeginInvoke(errorCode,nullptr,nullptr);
}

// Works fine.
void fireSyncEvent(System::String^ errorCode)
{
SyncEvent(errorCode);
}
};
 
BartMan said:
Opps a typo on my part the delegate was declared, and the event is
declared
below, and it has the same values, so I don't understand how it cannot
compile.
Especially since the c# works fine?

// Here is the Delegate:
public delegate bool MCDelegate(System::String^ errorCode);

public ref class MCEventTesting
{
public:
MCEventTesting(void);

event MCDelegate^ SyncEvent;
event MCDelegate^ AsyncEvent; // Async Event?????

public:
// Fire the event as an async event.
void fireErrorEventAsync(System::String^ errorCode)
{
// ERROR: "Complains that it must be a pointer to a member function."
MCDelegate^ delg = gcnew MCDelegate(this,&MCEventTesting::AsyncEvent);
AsyncEvent->BeginInvoke("test",nullptr,this);

// Also tried this, it didn't work complained that it needs to be a data
member.
// MCEventTesting::AsyncEvent->BeginInvoke(errorCode,nullptr,nullptr);
Click to expand...

Use this along with a custom event:

private:
MCDelegate^ AsyncHandlerList;

public:
event MCDelegate^ Async {
MCDelegate^ add(MCDelegate^ d) { return AsyncHandlerList =
Delegate::Combine(AsyncHandlerList, d); }
MCDelegate^ remove(MCDelegate^ d) { return AsyncHandlerList =
Delegate::Remove(AsyncHandlerList, d); }
}

void fireErrorEventAsync(System::String^ errorCode)
MCEventTesting::AsyncHandlerList->BeginInvoke(errorCode,nullptr,nullptr);
}
 
event MCDelegate^ Async {
MCDelegate^ add(MCDelegate^ d) { return AsyncHandlerList =
Delegate::Combine(AsyncHandlerList, d); }
MCDelegate^ remove(MCDelegate^ d) { return AsyncHandlerList =
Delegate::Remove(AsyncHandlerList, d); }
}
Click to expand...
Hello Ben,

Thanks for the reply. The above mentioned code issues the following error:
Error 1 error C3919: 'Async::add': function must have type 'void (MCDelegate
^)'

I tried changing it to "void add(MCDelegate^ d) {....}", but that didn't
seem to work either.
 
BartMan said:
Hello Ben,

Thanks for the reply. The above mentioned code issues the following
error:
Error 1 error C3919: 'Async::add': function must have type 'void
(MCDelegate
^)'

I tried changing it to "void add(MCDelegate^ d) {....}", but that didn't
seem to work either.
Click to expand...

also take out the word return. Oh, and the += and -= operators do work in
C++. Here's a snippet out of my own code:

virtual event System::EventHandler^ Closed

{

void add( System::EventHandler^ handler )

{

CloseHandlers += handler;

}

void remove( System::EventHandler^ handler )

{

CloseHandlers += handler;

}

}
 
also take out the word return. Oh, and the += and -= operators do work in
C++. Here's a snippet out of my own code:

virtual event System::EventHandler^ Closed

{

void add( System::EventHandler^ handler )

{

CloseHandlers += handler;

}

void remove( System::EventHandler^ handler )

{

CloseHandlers += handler;

}

}
Click to expand...

Thanks that is very good to know. I did not know that operator support has
been added in c++/clr. Thank for all your help, it is exactly what I needed.

Here is my final version which seems to execute properly.

public delegate bool MCDelegate(System::String^ errorCode);

public ref class MCEventTesting
{
public:
MCEventTesting(void);

event MCDelegate^ SyncEvent;

private:
MCDelegate^ AsyncHandlerList;

public:
event MCDelegate^ Async
{

void add(MCDelegate^ d)
{
AsyncHandlerList =
(MCDelegate^)System::Delegate::Combine(AsyncHandlerList, d);
}

void remove(MCDelegate^ d)
{
AsyncHandlerList = (MCDelegate^)System::Delegate::Remove(AsyncHandlerList,
d);
}
}

public:
void fireErrorEventAsync(System::String^ errorCode)
{
MCEventTesting::AsyncHandlerList->BeginInvoke(errorCode,nullptr,nullptr);
}

void fireSyncEvent(System::String^ errorCode)
{
SyncEvent(errorCode);
}
};
 
Thanks that is very good to know. I did not know that operator support
has
been added in c++/clr. Thank for all your help, it is exactly what I
needed.

Here is my final version which seems to execute properly.

public delegate bool MCDelegate(System::String^ errorCode);

public ref class MCEventTesting
{
public:
MCEventTesting(void);

event MCDelegate^ SyncEvent;

private:
MCDelegate^ AsyncHandlerList;

public:
event MCDelegate^ Async
{

void add(MCDelegate^ d)
{
AsyncHandlerList =
(MCDelegate^)System::Delegate::Combine(AsyncHandlerList, d);
Click to expand...
As I showed you with my code, this can be shortened to: AsyncHandlerList +=
d
}

void remove(MCDelegate^ d)
{
AsyncHandlerList = (MCDelegate^)System::Delegate::Remove(AsyncHandlerList,
d);
Click to expand...
And here, AsyncHandlerList -= d
}
}

public:
void fireErrorEventAsync(System::String^ errorCode)
{
MCEventTesting::AsyncHandlerList->BeginInvoke(errorCode,nullptr,nullptr);
Click to expand...
Don't forget to get the IAsyncResult and call EndInvoke later. And yes,
this is a pain, but it's required. You can pass an anonymous method as the
callback to BeginInvoke to help with this.
 
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