EventArgs.Empty Campo

Referência

Definição

Namespace:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Origem:: EventArgs.cs

Origem:: EventArgs.cs

Origem:: EventArgs.cs

Importante

Algumas informações se referem a produtos de pré-lançamento que podem ser substancialmente modificados antes do lançamento. A Microsoft não oferece garantias, expressas ou implícitas, das informações aqui fornecidas.

Fornece um valor para ser usado com eventos que não têm dados de evento.

public: static initonly EventArgs ^ Empty;

public static readonly EventArgs Empty;

 staticval mutable Empty : EventArgs

Public Shared ReadOnly Empty As EventArgs

Valor do campo

EventArgs

Exemplos

O exemplo a seguir mostra um aplicativo de contagem simples que gera um evento quando um limite é igual ou excedido. O Empty campo é passado para o OnThresholdReached método .

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

Comentários

Passe esse valor para manipuladores de eventos associados a eventos que não têm dados.

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