本文整理汇总了VB.NET中System.MulticastDelegate类的典型用法代码示例。如果您正苦于以下问题:VB.NET MulticastDelegate类的具体用法?VB.NET MulticastDelegate怎么用?VB.NET MulticastDelegate使用的例子?那么恭喜您, 这里精选的类代码示例或许可以为您提供帮助。
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示例1: StringContainer
' 导入命名空间
Imports System.Collections.Generic
Class StringContainer
' Define a delegate to handle string display.
Delegate Sub CheckAndPrintDelegate(ByVal str As String)
' A generic list object that holds the strings.
Private container As New List(Of String)()
' A method that adds strings to the collection.
Public Sub AddString(ByVal s As String)
container.Add(s)
End Sub
' Iterate through the strings and invoke the method(s) that the delegate points to.
Public Sub DisplayAllQualified(ByVal displayDelegate As CheckAndPrintDelegate)
For Each s In container
displayDelegate(s)
Next
End Sub
End Class
' This class defines some methods to display strings.
Class StringExtensions
' Display a string if it starts with a consonant.
Public Shared Sub ConStart(ByVal str As String)
If Not (str.Chars(0) = "a"c Or str.Chars(0) = "e"c Or str.Chars(0) = "i"c _
Or str.Chars(0) = "o"c Or str.Chars(0) = "u"c) Then
Console.WriteLine(str)
End If
End Sub
' Display a string if it starts with a vowel.
Public Shared Sub VowelStart(ByVal str As String)
If (str.Chars(0) = "a"c Or str.Chars(0) = "e"c Or str.Chars(0) = "i"c _
Or str.Chars(0) = "o"c Or str.Chars(0) = "u"c) Then
Console.WriteLine(str)
End If
End Sub
End Class
' Demonstrate the use of delegates, including the Remove and
' Combine methods to create and modify delegate combinations.
Class Test
Public Shared Sub Main()
' Declare the StringContainer class and add some strings
Dim container As New StringContainer()
container.AddString("this")
container.AddString("is")
container.AddString("a")
container.AddString("multicast")
container.AddString("delegate")
container.AddString("example")
' Create two delegates individually using different methods.
Dim constart As StringContainer.CheckAndPrintDelegate = AddressOf StringExtensions.ConStart
Dim vowelStart As StringContainer.CheckAndPrintDelegate = AddressOf StringExtensions.VowelStart
' Get the list of all delegates assigned to this MulticastDelegate instance.
Dim delegateList() As [Delegate] = conStart.GetInvocationList()
Console.WriteLine("conStart contains {0} delegate(s).", delegateList.Length)
delegateList = vowelStart.GetInvocationList()
Console.WriteLine("vowelStart contains {0} delegate(s).", delegateList.Length)
Console.WriteLine()
' Determine whether the delegates are System.Multicast delegates
If TypeOf conStart Is System.MulticastDelegate And TypeOf vowelStart Is System.MulticastDelegate Then
Console.WriteLine("conStart and vowelStart are derived from MulticastDelegate.")
Console.WriteLine()
End If
' Run the two single delegates one after the other.
Console.WriteLine("Executing the conStart delegate:")
container.DisplayAllQualified(conStart)
Console.WriteLine("Executing the vowelStart delegate:")
container.DisplayAllQualified(vowelStart)
Console.WriteLine()
' Create a new MulticastDelegate and call Combine to add two delegates.
Dim multipleDelegates As StringContainer.CheckAndPrintDelegate =
CType([Delegate].Combine(conStart, vowelStart),
StringContainer.CheckAndPrintDelegate)
' How many delegates does multipleDelegates contain?
delegateList = multipleDelegates.GetInvocationList()
Console.WriteLine("{1}multipleDelegates contains {0} delegates.{1}",
delegateList.Length, vbCrLf)
' Pass this mulitcast delegate to DisplayAllQualified.
Console.WriteLine("Executing the multipleDelegate delegate.")
container.DisplayAllQualified(multipleDelegates)
' Call remove and combine to change the contained delegates.
multipleDelegates = CType([Delegate].Remove(multipleDelegates, vowelStart),
StringContainer.CheckAndPrintDelegate)
multipleDelegates = CType([Delegate].Combine(multipleDelegates, conStart),
StringContainer.CheckAndPrintDelegate)
' Pass multipleDelegates to DisplayAllQualified again.
Console.WriteLine()
Console.WriteLine("Executing the multipleDelegate delegate with two conStart delegates:")
container.DisplayAllQualified(multipleDelegates)
End Sub
End Class
输出:
conStart contains 1 delegate(s). vowelStart contains 1 delegate(s). conStart and vowelStart are derived from MulticastDelegate. Executing the conStart delegate: This multicast delegate Executing the vowelStart delegate: is a example multipleDelegates contains 2 delegates. Executing the multipleDelegate delegate. This is a multicast delegate example Executing the multipleDelegate delegate with two conStart delegates: This This multicast multicast delegate delegate