如何：使用字典存储事件实例（C# 编程指南）

accessor-declarations 的一种用法是公开很多事件但不为每个事件分配字段，而是使用字典来存储这些事件实例。这只在具有很多事件但您预计大多数事件都不会实现时才有用。

public delegate void EventHandler1(int i);
public delegate void EventHandler2(string s);

public class PropertyEventsSample
{
    private System.Collections.Generic.Dictionary<string, System.Delegate> eventTable;

    public PropertyEventsSample()
    {
        eventTable = new System.Collections.Generic.Dictionary<string, System.Delegate>();
        eventTable.Add("Event1", null);
        eventTable.Add("Event2", null);
    }

    public event EventHandler1 Event1
    {
        add
        {
            lock (eventTable)
            {
                eventTable["Event1"] = (EventHandler1)eventTable["Event1"] + value;
            }
        }
        remove
        {
            lock (eventTable)
            {
                eventTable["Event1"] = (EventHandler1)eventTable["Event1"] - value;
            }
        }
    }

    public event EventHandler2 Event2
    {
        add
        {
            lock (eventTable)
            {
                eventTable["Event2"] = (EventHandler2)eventTable["Event2"] + value;
            }
        }
        remove
        {
            lock (eventTable)
            {
                eventTable["Event2"] = (EventHandler2)eventTable["Event2"] - value;
            }
        }
    }

    internal void RaiseEvent1(int i)
    {
        EventHandler1 handler1;
        if (null != (handler1 = (EventHandler1)eventTable["Event1"]))
        {
            handler1(i);
        }
    }

    internal void RaiseEvent2(string s)
    {
        EventHandler2 handler2;
        if (null != (handler2 = (EventHandler2)eventTable["Event2"]))
        {
            handler2(s);
        }
    }
}

public class TestClass
{
    public static void Delegate1Method(int i)
    {
        System.Console.WriteLine(i);
    }

    public static void Delegate2Method(string s)
    {
        System.Console.WriteLine(s);
    }

    static void Main()
    {
        PropertyEventsSample p = new PropertyEventsSample();

        p.Event1 += new EventHandler1(TestClass.Delegate1Method);
        p.Event1 += new EventHandler1(TestClass.Delegate1Method);
        p.Event1 -= new EventHandler1(TestClass.Delegate1Method);
        p.RaiseEvent1(2);

        p.Event2 += new EventHandler2(TestClass.Delegate2Method);
        p.Event2 += new EventHandler2(TestClass.Delegate2Method);
        p.Event2 -= new EventHandler2(TestClass.Delegate2Method);
        p.RaiseEvent2("TestString");

        // Keep the console window open in debug mode.
        System.Console.WriteLine("Press any key to exit.");
        System.Console.ReadKey();
    }
}
/* Output:
    2
    TestString
*/

请参阅

C# 编程指南

事件（C# 编程指南）

委托（C# 编程指南）