C#: Delegate and Event

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test.Other
{
    public class TestDelegateAndEvent
    {
        public delegate void TestDelegate();
        public event TestDelegate TestEventHandler;

        public void Test()
        {
            TestDelegate testDelegate = new TestDelegate(Test1);
            TestEventHandler += new TestDelegate(Test1);

            testDelegate();
            TestEventHandler();
        }
        public void Test1()
        {
        }
    }
}

TestDelegateAndEvent.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Test.Other
{
    class Program
    {
        //public static delegate void TestDelegate();
        //public static event TestDelegate TestEventHandler;
        static void Main(string[] args)
        {
            // Delegate can be triggered directly
            //TestDelegate testDelegate = new TestDelegate(Test);
            //testDelegate();

            //TestDelegateAndEvent test = new TestDelegateAndEvent();
            //test.TestEventHandler += Test;

            // Error: The delegate inner the class is private even if the type is public.
            // test.TestDelegate();

            // Error: Event can't be triggered directly.
            //test.TestEventHandler();

            Console.ReadLine();
        }

        public static void Test()
        {
            Console.WriteLine("test");
        }
    }
}

Program.cs

总结：

1. Delegate可以将方法作为另外一个方法的参数带入其中进行运算；

2. 实际上Delegate和Event都是类，Event是一种特殊类型的Delegate；

3. 类内的Delegate不能被对象调用，即便这个delegate是Public的；

4. delegate和event都重载了+=，-=， 但是delegate可以用=直接赋值，但是event不可以；

5. delegate和event都不能由对象直接触发；

6. delegate和event都不能是static.