我如何传递一组委托以运行到方法中

Question

Referencing the sample below, is there a way to pass the work done by GetType1s() and GetType2s() in on this constructor? I'm looking for something along the lines of a List <Action> so that I can just run each action iteratively from within the constructor without caring about what it does, but I can't think of an appropriate way to do that in which variables are set (and of different types). I realize this is getting awfully close to DI and IOC, so maybe there's no way out of creating a container if I want to pass this work into the class like this?

      public MainPageViewModel(string taskBaseLocation)
    {
        TasksBaseLocation = taskBaseLocation;
        Type1List = TasksModel.GetType1s(TasksBaseLocation);
        Type2List = TasksModel.GetType2s(TasksBaseLocation);
    }

Answer 1

Declare an appropriate delegate type and pass that in a generic list.

public delegate retType MyDelegate(param1type param1, param2type param2,...)

List<MyDelegate> listToPass = new List<MyDelegate>();

Answer 2

Since delegates are multicast, just pass an Action :

if(action != null) { action(); } 

and combine at the caller.

If you need to run them independently (for example, to run later actions even if earlier actions fail), de-construct it:

if(action != null)
{
    foreach(Action child in action.GetInvocationList())
    {
        try
        {
            child();
        }
        catch (Exception ex)
        {
             // handle/log etc
        }
    }
}

Note, however, that this doesn't magically provide access to the member variables from the delegate, unless the delegate's context already had access to the fields (and a reference to the new instance, perhaps via Action<T> instead of Action )

Answer 3

I have two approaches here, using pure lambdas or using Delegate.Combine. I'd prefer the lambda variety.

using System;
using System.Linq;

namespace X
{
    public class MyType
    {
        public delegate void DoInitialize(MyType instance);
        public int a,b,c;

        public MyType(DoInitialize initialize) 
        {
            initialize(this);
        }

        public MyType(params Action<MyType>[] initializers) 
        {
            foreach (var initializer in initializers)
                initializer(this);
        }

        public static void LambdaApproach()
        {
            var instance = new MyType(
                    i => i.a = 1,
                    i => i.b = 2,
                    i => i.c = 42);
            Console.WriteLine("{0}, {1}, {2}", instance.a, instance.b, instance.c);
        }

        public static void MulticastApproach()
        {
            var lambdas = new DoInitialize[] {
                    i => i.a = 1,
                    i => i.b = 2,
                    i => i.c = 42, };

            var instance = new MyType((DoInitialize) Delegate.Combine(lambdas.ToArray()));
            Console.WriteLine("{0}, {1}, {2}", instance.a, instance.b, instance.c);
        }

        public static void Main(string[] args)
        {
            LambdaApproach();
            MulticastApproach();
        }
    }

}