EventHandler EventHandler EventHandler EventHandler Delegate

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 Object Object Object

イベントのソース。The source of the event.

e
EventArgs EventArgs EventArgs 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
EventHandlerEventHandlerEventHandlerEventHandler
属性

次の例では、という名前のイベントThresholdReached関連付けられている、EventHandlerを委任します。The following example shows an event named ThresholdReached that is associated with an EventHandler delegate. 割り当てられているメソッド、EventHandlerでデリゲートが呼び出される、OnThresholdReachedメソッド。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 でのイベント モデルは、イベント デリゲートをイベントのハンドラーを関連付けることに基づきます。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のには、2 つの要素が必要です。To raise an event, two elements are needed:

  • イベントに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.

  • 必要に応じて、イベント データを提供する場合、イベント データを保持するクラスです。Optionally, a class that holds the event data, if the event provides data.

デリゲートは、署名、つまり、戻り値の型、メソッドのパラメーター リストの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することができます。You can use the delegate type to declare a variable that can refer to any method with the same signature as the delegate.

標準イベント ハンドラー デリゲートのシグネチャは、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イベントを発生させる、インスタンスを指しています。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が型から派生EventArgsとイベント データを保持します。Its second parameter is derived from type EventArgs and holds the event data. 2 番目のパラメーターの値だけは、イベントがイベント データを生成しない場合、EventArgs.Emptyフィールド。If the event does not generate event data, the second parameter is simply the value of the EventArgs.Empty field. 2 番目のパラメーターから派生した型は、それ以外の場合、EventArgsし、フィールドやイベント データを保持するために必要な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、定義済みのデリゲートを具体的にはデータを生成しないイベントのイベント ハンドラー メソッドを表します。The EventHandler delegate is a predefined delegate that specifically represents an event handler method for an event that does not generate data. ジェネリックを使用する場合は、イベントがデータを生成する必要がありますEventHandler<TEventArgs>クラスに委任します。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を使用してイベントを関連付けるには、イベントにデリゲートのインスタンスを追加します。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、次を参照してください。処理とイベントの発生します。For more information about event handler delegates, see Handling and Raising Events.

拡張メソッド

GetMethodInfo(Delegate) GetMethodInfo(Delegate) GetMethodInfo(Delegate) 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

こちらもご覧ください