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TypeFilter Delegate

Filters the classes represented in an array of Type objects.

Namespace:  System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

[<SerializableAttribute>]
[<ComVisibleAttribute(true)>]
type TypeFilter = 
    delegate of  
        m:Type * 
        filterCriteria:Object -> bool

Parameters

m
Type: System.Type

The Type object to which the filter is applied.

filterCriteria
Type: System.Object

An arbitrary object used to filter the list.

Return Value

Type: System.Boolean
true to include the Type in the filtered list; otherwise false.

The TypeFilter delegate is used to filter a list of classes. Specifically, you use it to filter the classes represented in an array of Type objects. The Type.FindInterfaces method uses this delegate to filter the list of interfaces that it returns. Every derived class of Delegate and MulticastDelegate has a constructor and a DynamicInvoke method. See the Visual C++ code example given in the description for Delegate.

This example shows how to define a method matching the TypeFilter delegate prototype allowing you to use reflection to filter or return a subset of matching entries.

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 three interfaces; 
'    Two are defined in this assembly. 
'    One is defined in another assembly. 
Public Class MyRetailer
    Implements IBookRetailer, IMusicRetailer, IComparable

    ' For demonstration purposes, this method returns nothing. 
    Public Function CompareTo(ByVal obj As Object) As Integer Implements System.IComparable.CompareTo
        Return Nothing 
    End Function 

    ' For demonstration purposes only, this method does nothing. 
    Public Sub ApplyDiscount() Implements IBookRetailer.ApplyDiscount
    End Sub 

    ' For demonstration purposes only, this method does nothing. 
    Public Sub Purchase() Implements IBookRetailer.Purchase
    End Sub 

    ' For demonstration purposes only, this method does nothing. 
    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 retailerType As Type = GetType(MyRetailer)
        Dim interfaces() As Type = _
            retailerType.FindInterfaces(AddressOf TypeFilter, retailerType.Assembly.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):")
        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 defined interface. 
    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 
' The example displays the following output: 
'    MyRetailer implements the following interfaces (defined in this assembly): 
'      IBookRetailer 
'      IMusicRetailer

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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