Question

I am using VB.Net. I have an object class called clsA(of T as clsB). Depending on what T is, I want to do different things. Let’s say that clsC and clsD both inherit clsB and therefore can be used for T.

If I have an instance of clsA(of clsC), how can I get the inside type (i.e. clsC) using reflection?

Answer 1

Reflection is a .NET technology – it’s not specific to either VB.NET or C#.

Given an object, o, use

o.GetType().GetGenericArguments()(0)

However, it’s probably a bad idea to explicitly vary your behavior based on the type. If you need to do different things based on class “A” vs. class “B”, then you should use virtual methods or properties, and override them in the derived types:

Public MustInherit Class BaseClass
    Public MustOverride Function OneMethodTwoWays() As Integer

    Public MustOverride ReadOnly Property OnePropertyTwoWays() As Integer

End Class

Public Class DerivedClass1
    Inherits BaseClass


    Public Overrides Function OneMethodTwoWays() As Integer
        Return 1 + 1
    End Function

    Public Overrides ReadOnly Property OnePropertyTwoWays() As Integer
        Get
            Return 1 + 1
        End Get
    End Property
End Class

Public Class DerivedClass2
    Inherits BaseClass

    Public Overrides Function OneMethodTwoWays() As Integer
        Return 2 * 1
    End Function

    Public Overrides ReadOnly Property OnePropertyTwoWays() As Integer
        Get
            Return 2 * 1
        End Get
    End Property
End Class

Public Class MyGeneric(Of T As BaseClass)
    Public Function DoTheyMatch(ByVal a As T, ByVal b As T) As Boolean
        Return a.OneMethodTwoWays() = b.OnePropertyTwoWays
    End Function
End Class