HOW TO：使用事件屬性處理多個事件

發行項
08/12/2011

若要使用事件屬性 (Visual Basic 2005 中的自訂事件)，您必須在引發事件的類別中定義事件屬性，然後在處理事件的類別中設定事件屬性的委派。若要在類別中實作多個事件屬性，該類別內部必須儲存及維護為每個事件所定義的委派。典型的方法是實作以事件索引鍵編製索引的委派集合。

如果要儲存每個事件的委派，您可以使用 EventHandlerList 類別，或只實作自己的集合。集合類別必須提供方法，根據事件索引鍵來設定、存取和擷取事件處理常式委派。例如，您可以使用 Hashtable 類別，或者從 DictionaryBase 類別衍生自訂類別。委派集合的實作詳細資料不需要公開至類別之外。

類別內的每個事件屬性，都會定義一個 add 存取子方法和一個 remove 存取子方法。事件屬性的 add 存取子會在委派集合中加入輸入委派執行個體。事件屬性的 remove 存取子會從委派集合中移除輸入委派執行個體。事件屬性存取子會使用事件屬性的預先定義索引鍵，從委派集合新增和移除執行個體。

若要使用事件屬性處理多重事件

在引發事件的類別內定義委派集合。
定義每個事件的索引鍵。
在引發事件的類別中定義事件屬性。
使用委派集合實作事件屬性的 add 和 remove 存取子方法。
使用公用事件屬性，在處理事件的類別中新增和移除事件處理常式。

範例

下列 C# 範例使用 EventHandlerList 儲存每個事件的委派，以實作 MouseDown 和 MouseUp 事件屬性。事件屬性建構的關鍵字是以粗體字表示。

注意事項
在 Visual Basic 2005 中不支援事件屬性。

' The class SampleControl defines two event properties, MouseUp and MouseDown.
Class SampleControl
    Inherits Component
    ' :
    ' Define other control methods and properties.
    ' :

    ' Define the delegate collection.
    Protected listEventDelegates As New EventHandlerList()

    ' Define a unique key for each event.
    Shared ReadOnly mouseDownEventKey As New Object()
    Shared ReadOnly mouseUpEventKey As New Object()

    ' Define the MouseDown event property.
    Public Custom Event MouseDown As MouseEventHandler
        ' Add the input delegate to the collection.
        AddHandler(Value As MouseEventHandler)
            listEventDelegates.AddHandler(mouseDownEventKey, Value)
        End AddHandler
        ' Remove the input delegate from the collection.
        RemoveHandler(Value As MouseEventHandler)
            listEventDelegates.RemoveHandler(mouseDownEventKey, Value)
        End RemoveHandler
        ' Raise the event with the delegate specified by mouseDownEventKey
        RaiseEvent(sender As Object, e As MouseEventArgs)
            Dim mouseEventDelegate As MouseEventHandler = _
                listEventDelegates(mouseDownEventKey)
            mouseEventDelegate(sender, e)
        End RaiseEvent
    End Event

    ' Define the MouseUp event property.
    Public Custom Event MouseUp As MouseEventHandler
        ' Add the input delegate to the collection.
        AddHandler(Value As MouseEventHandler)
            listEventDelegates.AddHandler(mouseUpEventKey, Value)
        End AddHandler
        ' Remove the input delegate from the collection.
        RemoveHandler(Value As MouseEventHandler)
            listEventDelegates.RemoveHandler(mouseUpEventKey, Value)
        End RemoveHandler
        ' Raise the event with the delegate specified by mouseDownUpKey
        RaiseEvent(sender As Object, e As MouseEventArgs)
            Dim mouseEventDelegate As MouseEventHandler = _
                listEventDelegates(mouseUpEventKey)
            mouseEventDelegate(sender, e)
        End RaiseEvent
    End Event
End Class

// The class SampleControl defines two event properties, MouseUp and MouseDown.
class SampleControl : Component
{
    // :
    // Define other control methods and properties.
    // :

    // Define the delegate collection.
    protected EventHandlerList listEventDelegates = new EventHandlerList();

    // Define a unique key for each event.
    static readonly object mouseDownEventKey = new object();
    static readonly object mouseUpEventKey = new object();

    // Define the MouseDown event property.
    public event MouseEventHandler MouseDown
    {
        // Add the input delegate to the collection.
        add
        {
            listEventDelegates.AddHandler(mouseDownEventKey, value);
        }
        // Remove the input delegate from the collection.
        remove
        {
            listEventDelegates.RemoveHandler(mouseDownEventKey, value);
        }
    }

    // Raise the event with the delegate specified by mouseDownEventKey
    private void OnMouseDown(MouseEventArgs e)
    {
        MouseEventHandler mouseEventDelegate =
            (MouseEventHandler)listEventDelegates[mouseDownEventKey];
        mouseEventDelegate(this, e);
    }

    // Define the MouseUp event property.
    public event MouseEventHandler MouseUp
    {
        // Add the input delegate to the collection.
        add
        {
            listEventDelegates.AddHandler(mouseUpEventKey, value);
        }
        // Remove the input delegate from the collection.
        remove
        {
            listEventDelegates.RemoveHandler(mouseUpEventKey, value);
        }
    }

    // Raise the event with the delegate specified by mouseUpEventKey
    private void OnMouseUp(MouseEventArgs e)
    {
        MouseEventHandler mouseEventDelegate =
            (MouseEventHandler)listEventDelegates[mouseUpEventKey];
        mouseEventDelegate(this, e);
    }
}

// The class SampleControl defines two event properties, MouseUp and MouseDown.
ref class SampleControl : Component
{
    // :
    // Define other control methods and properties.
    // :

    // Define the delegate collection.
protected:
    EventHandlerList^ listEventDelegates;

private:
    // Define a unique key for each event.
    static Object^ mouseDownEventKey = gcnew Object();
    static Object^ mouseUpEventKey = gcnew Object();

    // Define the MouseDown event property.
public:
    SampleControl()
    {
        listEventDelegates = gcnew EventHandlerList();
    }

    event MouseEventHandler^ MouseDown
    {
        // Add the input delegate to the collection.
        void add(MouseEventHandler^ value)
        {
            listEventDelegates->AddHandler(mouseDownEventKey, value);
        }
        // Remove the input delegate from the collection.
        void remove(MouseEventHandler^ value)
        {
            listEventDelegates->RemoveHandler(mouseDownEventKey, value);
        }
        // Raise the event with the delegate specified by mouseDownEventKey
        void raise(Object^ sender, MouseEventArgs^ e)
        {
            MouseEventHandler^ mouseEventDelegate =
                (MouseEventHandler^)listEventDelegates[mouseDownEventKey];
            mouseEventDelegate(sender, e);
        }
    }

    // Define the MouseUp event property.
    event MouseEventHandler^ MouseUp
    {
        // Add the input delegate to the collection.
        void add(MouseEventHandler^ value)
        {
            listEventDelegates->AddHandler(mouseUpEventKey, value);
        }
        // Remove the input delegate from the collection.
        void remove(MouseEventHandler^ value)
        {
            listEventDelegates->RemoveHandler(mouseUpEventKey, value);
        }
        // Raise the event with the delegate specified by mouseUpEventKey
        void raise(Object^ sender, MouseEventArgs^ e)
        {
            MouseEventHandler^ mouseEventDelegate =
                (MouseEventHandler^)listEventDelegates[mouseUpEventKey];
            mouseEventDelegate(sender, e);
        }
    }
};

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HOW TO：使用事件屬性處理多個事件

若要使用事件屬性處理多重事件

範例

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工作

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