EventArgs.Empty Champ

Référence

Définition

Espace de noms:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Source:: EventArgs.cs

Source:: EventArgs.cs

Source:: EventArgs.cs

Important

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Fournit une valeur à utiliser avec les événements qui n'ont pas de données d'événement.

public: static initonly EventArgs ^ Empty;

public static readonly EventArgs Empty;

 staticval mutable Empty : EventArgs

Public Shared ReadOnly Empty As EventArgs

Valeur de champ

EventArgs

Exemples

L’exemple suivant montre une application de comptage simple qui déclenche un événement lorsqu’un seuil est égal ou dépassé. Le Empty champ est passé à la OnThresholdReached méthode .

using System;

namespace ConsoleApplication1
{
    public class Program1
    {
        public static void Main()
        {
            Counter c = new(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 readonly 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)
        {
            ThresholdReached?.Invoke(this, e);
        }

        public event EventHandler? ThresholdReached;
    }
}

open System

type Counter(threshold) =
    let mutable total = 0

    let thresholdReached = Event<_>()

    member this.Add(x) =
        total <- total + x
        if total >= threshold then
            thresholdReached.Trigger(this, EventArgs.Empty)

    [<CLIEvent>]
    member _.ThresholdReached = thresholdReached.Publish

let c_ThresholdReached(sender, arg) =
    printfn "The threshold was reached."
    exit 0

let c = Counter(Random().Next 10)
c.ThresholdReached.Add c_ThresholdReached

printfn "press 'a' key to increase total"
while Console.ReadKey(true).KeyChar = 'a' do
    printfn "adding one"
    c.Add 1

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

Remarques

Transmettez cette valeur aux gestionnaires d’événements associés aux événements qui ne disposent pas de données.

S’applique à

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