FIM client Management Policy Rule

Hello, 

i try to use the fim client, but when i test this code to get MPR i have an error cannot cast RmResource to RmManagementPolicyRule

    String filtre = "/ManagementPolicyRule";
                    ///AuthenticationWorkflowDefinition

                    foreach (RmManagementPolicyRule mprNew in client.Enumerate(filtre))
                        //foreach (RmResource mprNew in client.Enumerate("/ManagementPolicyRule[DisplayName='# MPR - Action - User Calculate location reference']"))
                    {

                        Console.WriteLine(mprNew.DisplayName);
                        Console.ReadLine();
                    }

Any idea ?