EventHandler 代理人

定義

イベント データを持たないイベントを処理するメソッドを表します。Represents the method that will handle an event that has no event data.

public delegate void EventHandler(System::Object ^ sender, EventArgs ^ e);
[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public delegate void EventHandler(object sender, EventArgs e);
type EventHandler = delegate of obj * EventArgs -> unit
Public Delegate Sub EventHandler(sender As Object, e As EventArgs)

パラメーター

sender
Object

イベントのソース。The source of the event.

e
EventArgs

イベント データを含まないオブジェクト。An object that contains no event data.

継承
EventHandler
属性

次の例は、 ThresholdReached EventHandlerデリゲートに関連付けられているという名前のイベントを示しています。The following example shows an event named ThresholdReached that is associated with an EventHandler delegate. EventHandlerデリゲートに割り当てられているメソッドは、 OnThresholdReachedメソッドで呼び出されます。The method assigned to the EventHandler delegate is called in the OnThresholdReached method.

using namespace System;

public ref class ThresholdReachedEventArgs : public EventArgs
{
   public:
      property int Threshold;
      property DateTime TimeReached;
};

public ref class Counter
{
   private:
      int threshold;
      int total;

   public:
      Counter() {};

      Counter(int passedThreshold)
      {
         threshold = passedThreshold;
      }

      void Add(int x)
      {
          total += x;
          if (total >= threshold) {
             ThresholdReachedEventArgs^ args = gcnew ThresholdReachedEventArgs();
             args->Threshold = threshold;
             args->TimeReached = DateTime::Now;
             OnThresholdReached(args);
          }
      }

      event EventHandler<ThresholdReachedEventArgs^>^ ThresholdReached;

   protected:
      virtual void OnThresholdReached(ThresholdReachedEventArgs^ e)
      {
         ThresholdReached(this, e);
      }
};

public ref class SampleHandler
{
   public:
      static void c_ThresholdReached(Object^ sender, ThresholdReachedEventArgs^ e)
      {
         Console::WriteLine("The threshold of {0} was reached at {1}.",
                            e->Threshold,  e->TimeReached);
         Environment::Exit(0);
      }
};

void main()
{
   Counter^ c = gcnew Counter((gcnew Random())->Next(10));
   c->ThresholdReached += gcnew EventHandler<ThresholdReachedEventArgs^>(SampleHandler::c_ThresholdReached);

   Console::WriteLine("press 'a' key to increase total");
   while (Console::ReadKey(true).KeyChar == 'a') {
      Console::WriteLine("adding one");
      c->Add(1);
   }
}
using System;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Counter c = new Counter(new Random().Next(10));
            c.ThresholdReached += c_ThresholdReached;

            Console.WriteLine("press 'a' key to increase total");
            while (Console.ReadKey(true).KeyChar == 'a')
            {
                Console.WriteLine("adding one");
                c.Add(1);
            }
        }

        static void c_ThresholdReached(object sender, ThresholdReachedEventArgs e)
        {
            Console.WriteLine("The threshold of {0} was reached at {1}.", e.Threshold,  e.TimeReached);
            Environment.Exit(0);
        }
    }

    class Counter
    {
        private int threshold;
        private int total;

        public Counter(int passedThreshold)
        {
            threshold = passedThreshold;
        }

        public void Add(int x)
        {
            total += x;
            if (total >= threshold)
            {
                ThresholdReachedEventArgs args = new ThresholdReachedEventArgs();
                args.Threshold = threshold;
                args.TimeReached = DateTime.Now;
                OnThresholdReached(args);
            }
        }

        protected virtual void OnThresholdReached(ThresholdReachedEventArgs e)
        {
            EventHandler<ThresholdReachedEventArgs> handler = ThresholdReached;
            if (handler != null)
            {
                handler(this, e);
            }
        }

        public event EventHandler<ThresholdReachedEventArgs> ThresholdReached;
    }

    public class ThresholdReachedEventArgs : EventArgs
    {
        public int Threshold { get; set; }
        public DateTime TimeReached { get; set; }
    }
}
Module Module1

    Sub Main()
        Dim c As Counter = New Counter(New Random().Next(10))
        AddHandler c.ThresholdReached, AddressOf c_ThresholdReached

        Console.WriteLine("press 'a' key to increase total")
        While Console.ReadKey(True).KeyChar = "a"
            Console.WriteLine("adding one")
            c.Add(1)
        End While
    End Sub

    Sub c_ThresholdReached(sender As Object, e As ThresholdReachedEventArgs)
        Console.WriteLine("The threshold of {0} was reached at {1}.", e.Threshold, e.TimeReached)
        Environment.Exit(0)
    End Sub
End Module

Class Counter
    Private threshold As Integer
    Private total As Integer

    Public Sub New(passedThreshold As Integer)
        threshold = passedThreshold
    End Sub

    Public Sub Add(x As Integer)
        total = total + x
        If (total >= threshold) Then
            Dim args As ThresholdReachedEventArgs = New ThresholdReachedEventArgs()
            args.Threshold = threshold
            args.TimeReached = DateTime.Now
            OnThresholdReached(args)
        End If
    End Sub

    Protected Overridable Sub OnThresholdReached(e As ThresholdReachedEventArgs)
        RaiseEvent ThresholdReached(Me, e)
    End Sub

    Public Event ThresholdReached As EventHandler(Of ThresholdReachedEventArgs)
End Class

Class ThresholdReachedEventArgs
    Inherits EventArgs

    Public Property Threshold As Integer
    Public Property TimeReached As DateTime
End Class

注釈

.NET Framework のイベントモデルは、イベントをハンドラーに接続するイベントデリゲートを持つことに基づいています。The event model in the .NET Framework is based on having an event delegate that connects an event with its handler. イベントを発生させるには、次の2つの要素が必要です。To raise an event, two elements are needed:

  • イベントへの応答を提供するメソッドを識別するデリゲート。A delegate that identifies the method that provides the response to the event.

  • イベントがデータを提供する場合は、イベントデータを保持するクラス (オプション)。Optionally, a class that holds the event data, if the event provides data.

デリゲートは、メソッドのシグネチャ (戻り値の型とパラメーターリスト型) を定義する型です。The delegate is a type that defines a signature, that is, the return value type and parameter list types for a method. デリゲート型を使用して、デリゲートと同じシグネチャを持つ任意のメソッドを参照できる変数を宣言できます。You can use the delegate type to declare a variable that can refer to any method with the same signature as the delegate.

イベントハンドラーデリゲートの標準シグネチャは、値を返さないメソッドを定義します。The standard signature of an event handler delegate defines a method that does not return a value. このメソッドの最初のパラメーターは型Objectで、はイベントを発生させるインスタンスを参照します。This method's first parameter is of type Object and refers to the instance that raises the event. 2番目のパラメーターは、 EventArgs型から派生し、イベントデータを保持します。Its second parameter is derived from type EventArgs and holds the event data. イベントがイベントデータを生成しない場合、2番目のパラメーターは単にEventArgs.Emptyフィールドの値になります。If the event does not generate event data, the second parameter is simply the value of the EventArgs.Empty field. それ以外の場合、2番目のパラメーター EventArgsはから派生した型で、イベントデータを保持するために必要なフィールドまたはプロパティを提供します。Otherwise, the second parameter is a type derived from EventArgs and supplies any fields or properties needed to hold the event data.

EventHandlerデリゲートは、データを生成しないイベントのイベントハンドラーメソッドを明示的に表す、事前に定義されたデリゲートです。The EventHandler delegate is a predefined delegate that specifically represents an event handler method for an event that does not generate data. イベントによってデータが生成される場合は、 EventHandler<TEventArgs>汎用デリゲートクラスを使用する必要があります。If your event does generate data, you must use the generic EventHandler<TEventArgs> delegate class.

イベントを処理するメソッドにイベントを関連付けるには、デリゲートのインスタンスをイベントに追加します。To associate the event with the method that will handle the event, add an instance of the delegate to the event. デリゲートを削除しない限り、そのイベントが発生すると常にイベント ハンドラーが呼び出されます。The event handler is called whenever the event occurs, unless you remove the delegate.

イベントハンドラーデリゲートの詳細については、「イベントの処理と発生」を参照してください。For more information about event handler delegates, see Handling and Raising Events.

拡張メソッド

GetMethodInfo(Delegate)

指定したデリゲートによって表されるメソッドを表すオブジェクトを取得します。Gets an object that represents the method represented by the specified delegate.

適用対象

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