Question

请参阅以下代码：

  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

说我在应用程序中有这样的代码：

Dim s as Student = Student.Factory(somecriteria)

我如何根据Student.StudentFactory返回的内容，在运行时将s变量强制转换为PostGraduate或Undergraduate？

Answer 1

很难理解你想要在这里实现的目标，但要回答你的问题，你可以使用CType转换为具体的类和GetType来确定它要从哪个类开始用：

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

在运行时转换对象

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