[Answered ]-How do I implement the Signals (from Django) concept in C#

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What you are talking about here are typically handled as events in C#, for example;

public class SomeType {
    public event EventHandler SomeEvent;
    protected virtual void OnSomeEvent() {
        EventHandler handler = SomeEvent;
        if(handler!=null) handler(this,EventArgs.Empty);
    }
    public void SomethingInteresting() {
        // blah
        OnSomeEvent(); // notify subscribers
        // blap
    }
    // ...
}

With subscribers…

SomeType obj = new SomeType();
//...
obj.SomeEvent += /* some handler */
//...

the handler could be a method, but in your discussion of signatures etc, a common way of re-using existing methods with non-matching signatures is with anonymous methods:

obj.SomeEvent += delegate { this.Text = "Done!"; };

You can have a list of delegates:

List<SomeDelegateType> list = new List<SomeDelegateType>();
list.Add(...);

but this might be redundant because delegate instances are multicast – so you can do this more directly:

Action action = null;
action += delegate { Console.WriteLine("Did A");};
action += delegate { Console.WriteLine("Did B");};
action(); // does both A & B

Note that more complex delegate usage might involv incoming argument values – for example:

int i = 24;
Func<int,int,int> func = (x,y) => (x * i) + y;
int result = func(2, 3); // 51

By combining things like anonymous methods (or lambdas, as above) with captured variables, the issue of signatures having to match is rarely an issue – you can just wrap with a lambda to make the signature match (adding extra values or dropping arguments, as required).

Note that with events (in particular) the common approach is to keep the signature:

void SomeDelegateType(object sender, SomeArgsType args);

where SomeArgsType : EventArgs – or use EventHandler<T> which will do this for you.

👤Marc Gravell

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