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EventArgs.Empty Pole

  • Odwołanie

Definicja

Przestrzeń nazw:
System
Zestaw:
System.Runtime.dll
Zestaw:
mscorlib.dll
Zestaw:
netstandard.dll
Źródło:
EventArgs.cs
Źródło:
EventArgs.cs
Źródło:
EventArgs.cs

Udostępnia wartość do użycia ze zdarzeniami, które nie mają danych zdarzeń.

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

Wartość pola

EventArgs

Przykłady

W poniższym przykładzie pokazano prostą aplikację zliczaną, która zgłasza zdarzenie, gdy próg jest równy lub przekroczony. Pole Empty jest przekazywane do OnThresholdReached metody .

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;
    }
}

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

Uwagi

Przekaż tę wartość do programów obsługi zdarzeń skojarzonych ze zdarzeniami, które nie mają danych.

Dotyczy

Zobacz też