call a delegate from click event using C++/CLI - delegates

Question

In C#, We can call a new function from button click with arguments like this,
////My function
public static void Method1(int x)
{
Console.WriteLine("Method 1");
}
and set this function on click event of a command button like this,
button1.Click += delegate { mydelegate with argument };
Eg:
delegate void Procedure( int x);
public partial class Window1 : Window
{
public Window1()
{
Procedure pProcedure = new Procedure(Method1);
InitializeComponent();
button1.Click += delegate { pProcedure(10); };
}
public static void Method1(int x)
{
Console.WriteLine("Method 1");
}
}
Now when we click on the button1, then the function "Method1" will be invoke.
How can I do the same using C++/CLI?
I need to find the added delegate from the click event and need to remove. How can i do this?

Answer 1

If you're asking about how to use anonymous delegates in C++/CLI, then the answer is you can't. In C++/CLI, delegates must be bound to a named function.
To accomplish what inline anonymous delegates actually do in C#, you can use the concept of a 'functor' or function object. The following C++/CLI sample illustrates how to create a function object and "bind" it to a specific value and then show how to use it as an event subscriber.
using namespace System;
// Sample class with one event 'Started'
public ref class Widget
{
public:
Widget()
{
}
event EventHandler ^ Started;
void Start()
{
Console::WriteLine("Starting...");
Started(this, EventArgs::Empty);
}
};
// Declare 'functor' class to capture state
private ref class Functor
{
public:
Functor(int input)
: input_(input)
{
}
// This is what we will use as the handler method
void Handler(Object ^ sender, EventArgs ^ e)
{
Console::WriteLine(L"Invoked with input {0}.", input_);
}
private:
int input_;
};
// Entry point
int wmain(int argc, wchar_t ** argv)
{
// Create a functor to capture value '10'
Functor ^ f = gcnew Functor(10);
Widget ^ widget = gcnew Widget();
// Subscribe to event using functor's handler
// (note that we bind to the instance 'f' here)
EventHandler ^ handler = gcnew EventHandler(f, &Functor::Handler);
widget->Started += handler;
// Should print "Invoked with input 10."
widget->Start();
// Remove the handler
widget->Started -= handler;
// Should not print anything extra now
widget->Start();
return 0;
}

Answer 2

Thank you for your help.
With your help I can solve my problem.
The solution is like this,
//FirstWindow.h
#pragma once
using namespace System;
using namespace System::Windows;
using namespace System::Windows::Controls;
ref class Functor;
ref class FirstWindow : Window
{
Canvas^ maincanvas;
Button^ addbutton1;
Button^ addbutton2;
Functor^ pFunctor;
public:
FirstWindow(void);
void InitControls(void);
void MyFunction( int x, int y );
};
//FirstWindow.cpp
#include "FirstWindow.h"
#include "Functor.h"
FirstWindow::FirstWindow(void)
{
Title = "First Avalon App";
Width = 400;
Height = 400;
ResizeMode = System::Windows::ResizeMode::NoResize;
InitControls();
}
void FirstWindow::InitControls(void)
{
addbutton1 = gcnew Button();
addbutton1->Width = 80;
addbutton1->Height = 25;
addbutton1->Content = "Add";
pFunctor = gcnew Functor(this, 10, 20);
addbutton1->Click += gcnew RoutedEventHandler( pFunctor, &Functor::Handler);
Canvas::SetTop(addbutton1, 45);
Canvas::SetLeft(addbutton1, 200);
pFunctor = gcnew Functor(this, 100, 200);
addbutton2 = gcnew Button();
addbutton2->Width = 80;
addbutton2->Height = 25;
addbutton2->Content = "Add";
addbutton2->Click += gcnew RoutedEventHandler(pFunctor, &Functor::Handler);
Canvas::SetTop(addbutton2, 85);
Canvas::SetLeft(addbutton2, 200);
maincanvas = gcnew Canvas();
maincanvas->Children->Add(addbutton1);
maincanvas->Children->Add(addbutton2);
Content = maincanvas;
}
void FirstWindow::MyFunction( int x, int y )
{
MessageBox::Show("This function is call by Button Click with values " + x.ToString() + " , " + y.ToString() );
}
//Functor.h
#pragma once
using namespace System;
using namespace System::Windows;
using namespace System::Windows::Controls;
ref class FirstWindow;
private ref class Functor
{
public:
Functor(FirstWindow^ pFirstWindow, int pFirstArg, int pSecArg);
// This is what we will use as the handler method
void Handler(Object ^ sender, RoutedEventArgs ^ e);
private:
int m_pFirstArg;
int m_pSecArg;
FirstWindow^ m_pFirstWindow;
};
//Functor.cpp
#include "Functor.h"
#include "FirstWindow.h"
Functor::Functor(FirstWindow^ pFirstWindow, int pFirstArg, int pSecArg) : m_pFirstWindow( pFirstWindow ), m_pFirstArg(pFirstArg), m_pSecArg( pSecArg )
{
}
void Functor::Handler(Object ^ sender, RoutedEventArgs ^ e)
{
if ( m_pFirstWindow )
m_pFirstWindow->MyFunction(m_pFirstArg, m_pSecArg );
}
Now when we click on button one, then the application call the function "MyFunction" with value 10,20 and when we click on button 2 then the same function "MyFunction" with value 100,200.
Thank you for your help.
Sabeesh