Type.FindInterfaces Method

Returns an array of Type objects representing a filtered list of interfaces implemented or inherited by the current Type.

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

Public Overridable Function FindInterfaces ( _
	filter As TypeFilter, _
	filterCriteria As Object _
) As Type()
Dim instance As Type
Dim filter As TypeFilter
Dim filterCriteria As Object
Dim returnValue As Type()

returnValue = instance.FindInterfaces(filter, filterCriteria)
public Type[] FindInterfaces (
	TypeFilter filter, 
	Object filterCriteria
public function FindInterfaces (
	filter : TypeFilter, 
	filterCriteria : Object
) : Type[]
Not applicable.



The TypeFilter delegate that compares the interfaces against filterCriteria.


The search criteria that determines whether an interface should be included in the returned array.

Return Value

An array of Type objects representing a filtered list of the interfaces implemented or inherited by the current Type, or an empty array of type Type if no interfaces matching the filter are implemented or inherited by the current Type.

Exception typeCondition


filter is a null reference (Nothing in Visual Basic).


A static initializer is invoked and throws an exception.

This method can be overridden by a derived class.

The Module.FilterTypeName and Module.FilterTypeNameIgnoreCase delegates supplied by the System.Reflection.Module class may also be used, in lieu of the System.Reflection.TypeFilter delegate.

All of the interfaces implemented by this class are considered during the search, whether declared by a base class or this class itself.

This method searches the base class hierarchy, returning each of the matching interfaces each class implements as well as all the matching interfaces each of those interfaces implements (that is, the transitive closure of the matching interfaces is returned). No duplicate interfaces are returned.

If the current Type represents a type parameter in the definition of a generic type or generic method, FindInterfaces searches all the interfaces declared in the constraints on the type parameter, and all interfaces inherited through the interfaces declared in the constraints. If the current Type represents a type argument of a generic type, FindInterfaces searches all the interfaces implemented by the type, whether or not they match constraints.


FindInterfaces can return generic interfaces, even on types that are not generic. For example, a nongeneric type might implement IEnumerable<int> (IEnumerable(Of Integer) in Visual Basic).

The following example finds the specified interface implemented or inherited by the specified type, and then displays the interface names.

Imports System
Imports System.Xml
Imports System.Reflection
Imports Microsoft.VisualBasic

Public Class MyFindInterfacesSample
    Public Shared Sub Main()
            Dim myXMLDoc As New XmlDocument()
            myXMLDoc.LoadXml("<book genre='novel' ISBN='1-861001-57-5'>" _
                & "<title>Pride And Prejudice</title>" & "</book>")
            Dim myType As Type = myXMLDoc.GetType()

            ' Specify the TypeFilter delegate that compares the 
            ' interfaces against filter criteria.
            Dim myFilter As New TypeFilter(AddressOf MyInterfaceFilter)
            Dim myInterfaceList() As String = _
                {"System.Collections.IEnumerable", _
            Dim index As Integer
            For index = 0 To myInterfaceList.Length - 1
                Dim myInterfaces As Type() = _
                    myType.FindInterfaces(myFilter, myInterfaceList(index))
                If myInterfaces.Length > 0 Then
                    Console.WriteLine(ControlChars.Cr & _
                        "{0} implements the interface {1}.", _
                        myType, myInterfaceList(index))
                    Dim j As Integer
                    For j = 0 To myInterfaces.Length - 1
                        Console.WriteLine("Interfaces supported: {0}", _
                    Next j
                    Console.WriteLine(ControlChars.Cr & _
                        "{0} does not implement the interface {1}.", _
                        myType, myInterfaceList(index))
                End If
            Next index
        Catch e As ArgumentNullException
            Console.WriteLine("ArgumentNullException: " & e.Message)
        Catch e As TargetInvocationException
            Console.WriteLine("TargetInvocationException: " & e.Message)
        Catch e As Exception
            Console.WriteLine("Exception: " & e.Message)
        End Try
    End Sub 'Main
    Public Shared Function MyInterfaceFilter(ByVal typeObj As Type, _
        ByVal criteriaObj As [Object]) As Boolean
        If typeObj.ToString() = criteriaObj.ToString() Then
            Return True
            Return False
        End If
    End Function 'MyInterfaceFilter 
End Class 'MyFindInterfacesSample

import System.*;
import System.Xml.*;
import System.Reflection.*;

public class MyFindInterfacesSample
    public static void main(String[] args)
        try {
            XmlDocument myXmlDoc = new XmlDocument();
            myXmlDoc.LoadXml("<book genre='novel' ISBN='1-861001-57-5'>"
                + "<title>Pride And Prejudice</title>" + "</book>");
            Type myType = myXmlDoc.GetType();
            // Specify the TypeFilter delegate that compares the interfaces 
            // against filter criteria.
            TypeFilter myFilter = new TypeFilter(MyInterfaceFilter);
            String myInterfaceList[] = new String[] { 
                "System.Collections.ICollection" };
            for (int index = 0; index < myInterfaceList.length; index++) {
                Type myInterfaces[] = myType.FindInterfaces(myFilter,
                if (myInterfaces.length > 0) {
                    Console.WriteLine("\n{0} implements the interface {1}.",
                        myType, myInterfaceList.get_Item(index));
                    for (int j = 0; j < myInterfaces.length; j++) {
                        Console.WriteLine("Interfaces supported: {0}.",
                else {
                    Console.WriteLine("\n{0} does not implement the"
                        + " interface {1}.", myType,
        catch (ArgumentNullException e) {
            Console.WriteLine("ArgumentNullException: " + e.get_Message());
        catch (TargetInvocationException e) {
            Console.WriteLine("TargetInvocationException: " + e.get_Message());
        catch (System.Exception e) {
            Console.WriteLine("Exception: " + e.get_Message());
    } //main

    public static boolean MyInterfaceFilter(Type typeObj, Object criteriaObj)
        if (typeObj.ToString().Equals(criteriaObj.ToString())) {
            return true;
        else {
            return false;
    } //MyInterfaceFilter
} //MyFindInterfacesSample

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0