Collection of functions

Question

in my csharp application i have certain events which should trigger functions to be called on a specific thread, which is looping through some code.

now, instead of storing all this data by hand and having a big switch-case i was wondering if it is possible to store these functions and their paramteres in a list which is then processed by the other thread?

pseudo code:

var func = pointer2somefunction(13, "abc");
list.add(func);

other thread:

while (list.Count > 0)
{
     var func = list.Remove(0);
     func.Invoke();
}

Answer 1

Yes, you can do this by using a List<Action> or a Queue<Action> which suits slightly better in my opinion. Action is a type for a no-parameter void delegate:

var functions = new Queue<Action>();

functions.Enqueue(() => Console.WriteLine("Foo"));
functions.Enqueue(() => Console.WriteLine("Bar"));

while (functions.Any())
{
    // note the double parenthesis here: one for Dequeue
    // and one for your dequeued function
    functions.Dequeue()();
}

If you need parameters, use Action<T> for one, Action<T, T> for two and so forth. For a return value, use Func instead of Action (or Func<T> etc.).

Maybe an event would help you too. Events are C#'s language feature to use the observer pattern.

// events are usually on the instance rather than static
private static event EventHandler MyEvent;

static void Main(string[] args)
{
    MyEvent += (s, e) => Console.WriteLine("FooEvent");
    MyEvent += (s, e) => Console.WriteLine("BarEvent");
    MyEvent(null, EventArgs.Empty);
}

An event is a multicast delegate, which is a delegate to a list of functions. You cannot control the threading for each handler though: Unlike the Queue<Action> above, where you can start or reuse threads, a multicast delegate is exposed as one call from outside, letting you use only one thread for all invocations.

Answer 2

I think you are implementing events in that way. You don't need a big switch case, you need several events, and then trigger the right event in the right time, and register it with the right method.

You can do a list of delegates, but it'll start getting complicated when you want different function with different set of parameters.