Passing a callback function to another class

Question

I\'m basically trying to pass a method to another class to be called later, but can\'t quite figure this out in C# (I\'m still too used to Objective-C).

public c         


        

Answer 1

You can pass it as Action<string> - which means it is a method with a single parameter of type string that doesn't return anything (void) :

public void DoRequest(string request, Action<string> callback)
{
    // do stuff....
    callback("asdf");
}

Answer 2

You could use only delegate which is best for callback functions:

public class ServerRequest
{
    public delegate void CallBackFunction(string input);

    public void DoRequest(string request, CallBackFunction callback)
    {
        // do stuff....
        callback(request);
    }
}

and consume this like below:

public class Class1
    {
        private void btn_click(object sender, EventArgs e)
        {
            ServerRequest sr = new ServerRequest();
            var callback = new ServerRequest.CallBackFunction(CallbackFunc);
            sr.DoRequest("myrequest",callback);
        }

        void CallbackFunc(string something)
        {

        }


    }

Answer 3

You could change your code in this way:

public delegate void CallbackHandler(string str);

public class ServerRequest
{
    public void DoRequest(string request, CallbackHandler callback)
    {
        // do stuff....
        callback("asdf");
    }
}

Answer 4

What you need is a delegate and a callback. Here is a nice MSDN article that will show you how to use this technique in C#.

Answer 5

You have to first declare delegate's type because delegates are strongly typed:

public void MyCallbackDelegate( string str );

public void DoRequest(string request, MyCallbackDelegate callback)
{
     // do stuff....
     callback("asdf");
}

Answer 6

public class Class1
    {

        private void btn_click(object sender, EventArgs e)
        {
            ServerRequest sr = new ServerRequest();
            sr.Callback += new ServerRequest.CallbackEventHandler(sr_Callback);
            sr.DoRequest("myrequest");
        }

        void sr_Callback(string something)
        {

        }


    }

    public class ServerRequest
    {
        public delegate void CallbackEventHandler(string something);
        public event CallbackEventHandler Callback;   

        public void DoRequest(string request)
        {
            // do stuff....
            if (Callback != null)
                Callback("bla");
        }
    }