using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        new C().Test();

    }

}

​

public class C

{

    public void Test()

    {

        var dict = new Dictionary<string, Action>();

        dict["foo"] = SomeMethod;

        dict.Dump();

        Action action = dict["foo"];

        action -= SomeMethod;

        dict.Dump();

        dict["foo"] -= SomeMethod;

        dict.Dump();

    }

    public void SomeMethod() => Console.WriteLine("Called");

}