EventArgs.Empty EventArgs.Empty EventArgs.Empty EventArgs.Empty Field

Definizione

Fornisce un valore da utilizzare con eventi che non dispongono di dati.Provides a value to use with events that do not have event data.

public: static initonly EventArgs ^ Empty;
public static readonly EventArgs Empty;
 staticval mutable Empty : EventArgs
Public Shared ReadOnly Empty As EventArgs 

Valore del campo

Esempi

Nell'esempio seguente viene illustrata una semplice applicazione di conteggio che genera un evento quando viene equaled o supera una soglia.The following example shows a simple counting application that raises an event when a threshold is equaled or exceeded. Il Empty campo viene passato per il OnThresholdReached (metodo).The Empty field is passed to the OnThresholdReached method.

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, EventArgs e)
        {
            Console.WriteLine("The threshold was reached.");
            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)
            {
                OnThresholdReached(EventArgs.Empty);
            }
        }

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

        public event EventHandler ThresholdReached;
    }
}
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 EventArgs)
        Console.WriteLine("The threshold was reached.")
        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
            OnThresholdReached(EventArgs.Empty)
        End If
    End Sub

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

    Public Event ThresholdReached As EventHandler
End Class

Commenti

Passare questo valore per i gestori eventi associati agli eventi che non sono presenti dati.Pass this value to event handlers that are associated with events that do not have data.

Si applica a

Vedi anche