Delegado TypeFilter

Imports system
Imports system.Reflection

' This interface is defined in this assembly.
Public Interface IBookRetailer
    Sub Purchase()
    Sub ApplyDiscount()
End Interface

' This interface is also defined in this assembly.
Public Interface IMusicRetailer
    Sub Purchase()
End Interface

' This class implements four interfaces; two are defined in this assembly and two are defined in another assembly.
Public Class MyRetailer
    Implements IBookRetailer, IMusicRetailer, IComparable, ICloneable

    ' For demonstration purposes, this method returns nothing; it just allows the code to compile.
    Public Function Clone() As Object Implements System.ICloneable.Clone
        Return Nothing
    End Function

    ' For demonstration purposes, this method returns nothing; it just allows the code to compile.
    Public Function CompareTo(ByVal obj As Object) As Integer Implements System.IComparable.CompareTo
        Return Nothing
    End Function

    ' For demonstration purposes, this method returns nothing; it just allows the code to compile.
    Public Sub ApplyDiscout() Implements IBookRetailer.ApplyDiscount
    End Sub

    ' For demonstration purposes, this method returns nothing; it just allows the code to compile.
    Public Sub Purchase() Implements IBookRetailer.Purchase
    End Sub

    ' For demonstration purposes, this method returns nothing; it just allows the code to compile.
    Public Sub Purchase1() Implements IMusicRetailer.Purchase
    End Sub
End Class

Module Module1

    Sub Main()
        ' Find the interfaces defined by the MyRetailer class. Each interface found is passed to
        ' the TypeFilter method which checks if the interface is defined in the executing assembly.
        Dim interfaces() As Type = _
            GetType(MyRetailer).FindInterfaces(AddressOf TypeFilter, Assembly.GetExecutingAssembly().GetName().ToString())

        ' Show the interfaces that are defined in this assembly that are also implemented by MyRetailer.
        Console.WriteLine("MyRetailer implements the following interfaces (defined in this assembly):")
        Dim t As Type
        For Each t In interfaces
            Console.WriteLine("   {0}", t.Name)
        Next
    End Sub

    ' This method is called by the FindInterfaces method. 
    ' This method is called once per interface defined.
    Function TypeFilter(ByVal t As Type, ByVal filterCriteria As Object) As Boolean
        ' Return true if interface is defined in the same 
        ' assembly identified by the filterCriteria object.
        Return t.Assembly.GetName().ToString() = CType(filterCriteria, String)
    End Function

End Module

' Output will vary based on the contents of the C drive.
'
' This code produces the following output.
' MyRetailer implements the following interfaces (defined in this assembly):
'   IBookRetailer
'   IMusicRetailer