单项选择题 YouarecreatingaWindowsFormsApplicationbyusingthe.NETFramework3.5.Usersusetheapplicationtoprocessandapproveinvoices.AlistofrecentlyaccessedinvoicesisstoredintheuserssettingssectionoftheApp.configfile.Youneedtomaintainthelistofinvoicesfromthelastpersistedstate.Whatshouldyoudo？（）

单项选择题 You are creating a Windows Forms application by using the .Net Framework 3.5.You create an instance of a Backgroundworker component named backgroundWorker1 to process operations that take a long time.You discover that when the application attempts to report the progress，you receive a System.InvalidOperationException exception when executing  thebackgroundWorker1.ReportProgress method.You need to configure the BackgroundWorker component appropriately to prevent the application from generating exceptions.    What should yo do？（）

单项选择题 You are creating a Windows Forms Application by using the .NET Framework 3.5.You plan to design a new control that will be used on multiple forms in the app.You need to ensure that the control meets the following requirement：   （1）It retrieves data from a MSSQL Server 2008 database instance.   （2）It uses WPF classes to display data.   （3）It uses user-customizable actions when the control is first painted on the form.    What should you do？（）