在运行时投射对象

Question

请参见下面的代码：

  Public Class Student
    Public Shared Function Factory(ByVal somecriteria As String) As Student
        'Return either a PostGraduate or UnderGraduate based on some criteria
    End Function
End Class

Public Class PostGraduate
    Inherits Student

End Class

Public Class UnderGraduate
    Inherits Student

End Class

假设我在应用程序中有一些这样的代码：

Dim s as Student = Student.Factory(somecriteria)

我如何在运行时将s变量转换为PostGraduate或Undergraduate，这取决于Student.StudentFactory返回的内容？

Answer 1

很难理解您要在此处实现的目标，但是要回答您的问题，您只能使用CType转换为具体的类，而使用GetType来确定GetType哪种类型的类开始：

Dim s As Student = Student.Factory("")
If s.GetType Is GetType(PostGraduate) Then
    Dim p As PostGraduate = CType(s, PostGraduate)
Else
    Dim u As UnderGraduate = CType(s, UnderGraduate)
End If