WinForm事件訂閱到另一個類

Question

public partial class Form1 : Form 
{ 
    private EventThrower _Thrower; 

    public Form1() 
    { 
     InitializeComponent(); 
    } 

    private void DoSomething() 
    { 
     MessageBox.Show("It worked"); 
    } 

    private void button1_Click(object sender, EventArgs e) 
    { 
     _Thrower = new EventThrower(); 
     //using lambda expression..need to use .NET2 so can't use this. 
     _Thrower.ThrowEvent += (sender2, args) => { DoSomething(); }; 

     var eventThrower = new EventThrower(); 
     eventThrower.test(); 
    } 
} 

public class EventThrower 
{ 
    public delegate void EventHandler(object sender, EventArgs args); 
    public event EventHandler ThrowEvent = delegate { }; 

    public void SomethingHappened() 
    { 
     ThrowEvent(this, new EventArgs()); 
    } 

    public void test() 
    { 
     System.Threading.Thread.Sleep(1000); 
     SomethingHappened(); 
    } 
} 

我想讓我的winform用戶界面訂閱EventThrower類中的事件。 DoSomething永遠不會發生。

How to subscribe to other class' events in c#?

Answer 1

這是因爲你在調用測試之前創建一個新的EventThrower。

如果更改：

var eventThrower = new EventThrower(); 
    eventThrower.test(); 

到：

_Thrower.test(); 

它將調用DoSomething的。

Answer 2

事件不是靜態的，EventHandler的一個實例存在每個實例的EventThrower。

您訂閱事件上_Thrower，但你創建的EventThrower一個新的實例，並在調用test()該實例。您從未訂閱過該實例的事件，因此您的處理程序無法運行。

它應該是：

_Thrower.ThrowEvent += (sender2, args) => { DoSomething(); }; 
_Thrower.test();