C# passing extra parameters to an event handler?

Question

Let say, I want to pass some extra data when assigning an event handler. Consider the following code:

private void setup(string someData)
{
     Object.assignHandler(evHandler);
}

public void evHandler(Object sender)
{
    // need someData here!!!
}

How would I go about getting someData into my evHandler method?

Answer 1

Captured variables:

private void setup(string someData)
{
    Object.assignHandler((sender,args) => {
        evHandler(sender, someData);
    });
}

public void evHandler(Object sender, string someData)
{
    // use someData here
}

Or (C# 2.0 alternative):

    Object.assignHandler((EventHandler)delegate(object sender,EventArgs args) {
        evHandler(sender, someData);
    });

Answer 2

My question that was similar was marked a duplicate so thought I'd add an answer here since it won't let me on my question.

class Program
    {
        delegate void ComponentEventHandler(params dynamic[] args);

        event ComponentEventHandler onTest;

        static void Main(string[] args)
        {  
            Program prg = new Program();

            // can be bound to event and called that way
            prg.onTest += prg.Test;
            prg.onTest.Invoke("What", 5, 12.0);

            Console.ReadKey();
        }

        public void Test(params dynamic[] values)
        {
            // assign our params to variables
            string name = values[0];
            int age = values[1];
            double value = values[2];

            Console.WriteLine(name);
            Console.WriteLine(age);
            Console.WriteLine(value);
        }
    }

Answer 3

You could create a custom object having additional properties based on Object:

class CustomObject : Object
{
    public string SomeData;
}

private void setup(string someData)
{
    CustomObject customObject = new CustomObject { SomeData = someData };
    CustomObject.assignHandler(evHandler);
}

public void evHandler(Object sender)
{
    string someData = ((CustomObject)sender).SomeData;
}

If the data should not be changed anymore after initialization, you could also add a custom constructor, for example.

Answer 4

you can try doing this:

string yourObject;

theClassWithTheEvent.myEvent += (sender, model) =>
{
 yourObject = "somthing";
}

Answer 5

private void setup(string someData)
{
     Object.assignHandler((sender) => evHandler(sender,someData));
}
public void evHandler(Object sender, string someData)
{
    // need someData here!!!
}

Answer 6

Well, the simplest method id to make someData a member variable like so:

public class MyClass
{
    private string _eventData;

    private void setup(string someData) 
    {
       _eventData = someData;
       Object.assignHandler(evHandler);
    }

    public void evHandler()
    {
        // do something with _eventData here
    }
}

I'm not sure that's the best way to do it, but it really depends on the event type, the object, etc.