我如何为AddressOf CalledBack添加代理？

Question

尝试尝试或两次添加委托...不成功。

   Public Function CallbackAddress() As Integer
  'UPGRADE_WARNING: Add a delegate for AddressOf CalledBack Click for more: 'ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?keyword="E9E157F7-EF0C-4016-87B7-7D7FBBC6EE08"'
    CallbackAddress = GetAddress(AddressOf CalledBack)
    End Function

    Private Function GetAddress(ByVal address As Integer) As Integer
        'GetAddress = address
        Return address
    End Function

这里是添加委托的失败（不完整或完全错误）的尝试：

  Public Delegate Sub CalledBackDelegate(ByVal param As Integer)

  Public Function CallbackAddress() As Integer
        Dim myCalledBackDelegate As CalledBackDelegate = New CalledBackDelegate(AddressOf CalledBack)
        CallbackAddress = GetAddress(myCalledBackDelegate)  // << This doesn't work! 
    End Function

仍然以错误结束。 myCalledbackDegate无法转换为整数。我想念什么？

Answer 1

建议的所有三个函数都是返回整数的函数。虽然当然可以有一个函数返回一个委托，但是有一个返回fixed委托的函数将毫无意义。

委托是对函数的引用，用于在调用站点不知道将调用哪种方法的情况下调用函数。现在，这通常是通过lambda函数完成的。下面是一个完整的应用程序，显示了当今如何普遍使用委托和lambda（一种特殊类型的委托）。您的示例缺少用法，因此我们无法真正为您提供帮助。希望这有助于阐明概念。 （请使用iPad调整布局）。

imports System

Public Module Module1
  Public Sub Main()

    console.Write("Enter a number:")
    Dim x as integer = if(integer.tryparse(console.ReadLine().trim, x), x, x)
    console.Write("Enter another number:")
    dim y as integer = if(integer.tryparse(console.ReadLine().trim, y), y, y)

    console.Write("Enter a plus or minus sign:")

    dim operation = console.ReadLine().Trim()

    dim op as func(Of integer, integer, integer)

    select case operation

        case "+"

            op = addressof add

        case "-"

            op = addressof minus

    end Select

    console.WriteLine($"Result of {x} {operation} {y} is {op(x, y)}")

    dim lambda as func(of integer)

    select case operation

        case "+"

            lambda = function() x + y

        case "-"

            lambda = function() x - y

    end select 
    console.writeline($"Result of {x} {operation} {y} is {lambda()}")

  End Sub
  public Function Add(x as integer, y as integer) as integer

    return x + y

  end Function

  public function Minus(x as integer, y as integer) as integer
    return x - y
  end function
End Module