VB.NET：如何处理变量类型参数和返回值？

问题描述

| 是否可以替换这两个功能

Function f1 (s As String) As class1()
  Dim a() As String = Split(s)
  Dim b(UBound(a)) As class1
  For i As Integer = 0 To UBound(a)
    b(i) = New class1(a(i))
  Next
  f1 = b
End Function

和

Function f2 (s As String) As class2()
  Dim a() As String = Split(s)
  Dim b(UBound(a)) As class2
  For i As Integer = 0 To UBound(a)
    b(i) = New class2(a(i))
  Next
  f2 = b
End Function

具有类似的通用功能

Function fGeneric (s As String,T As Type) As T()
  Dim a() As String = Split(s)
  Dim b(UBound(a)) As T
  For i As Integer = 0 To UBound(a)
    b(i) = New T(a(i))
  Next
  fGeneric = b
End Function

？ 解

Class class1
  Private _Name As String
  Public ReadOnly Property Name As String
    Get
      Name = _Name
    End Get
  End Property
  Sub New(s As String)
    _Name = s
  End Sub
End Class

Function fGeneric(Of T) (s As String) As IEnumerable(Of T)
  Dim a() As String = Split(s)
  Dim b(UBound(a)) As T
  For i As Integer = 0 To UBound(a)
    b(i) = GetType(T).InvokeMember( _
      Nothing,_
      BindingFlags.DeclaredOnly Or _
      BindingFlags.Public Or _
      BindingFlags.NonPublic Or _
      BindingFlags.Instance Or _
      BindingFlags.CreateInstance,_
      Nothing,_
      New Object(){a(i)} _
    )
  Next
  fGeneric = b
End Function

Response.Write(fGeneric(Of class1)(\"a b c\")(1).Name)

输出

b

    

解决方法

Function fGeneric(Of T) (ByVal s As String,ByVal createT As Func(Of String,T)) As IEnumerable(Of T)
  Return Split(s).Select(Function(a) createT(a))
End Function

这样称呼它

fGeneric(Of class1)(\"some,string,value\",Function(a) Return New class1(a))

    ,正如@Joel指出的那样，可以使用linq很好地解决此问题，但为了接近@ ic3b3rg的问题，语法应为：

Function fGeneric(Of T As New) (s As String,createT As Func(Of String,T)) As T()
  Dim a() As String = Split(s)
  Dim b(UBound(a)) As T
  For i As Integer = 0 To UBound(a)
    b(i) = createT(a(i))
  Next
  fGeneric = b
End Function

fGeneric(Of class1)(\"some,Function(a) Return New class1(a))

编辑 仔细研究一下，我认为这不会奏效，因为我们从来没有说过可以从10英镑中构造出9英镑。我们只说过可以用

new

创建

T

。我不知道如何解决...欢迎任何建议（随时进行编辑）。     ,看一下思考。我认为它可以帮助您获得与示例更紧密相关的结果。