单项选择题
A.Cancel the background process in the backgroundworker1_DoWork event
B.Set the IsBusy property og backgroundworker1 to True before you attempt to cancel
C.Set the WorkerSupportsCancellation property of backgroundworker1 to true before the code
D.Set the DoWorkEventArgs Cancel property to true
单项选择题 YouarecreatingaWindowsFormsapplicationbyusingthe.NetFramework3.5.Youplantodesignacompositecontrolfortheapplication.Youneedtoderivethecontrolfromabaseclassthatsupportstemplates.Whatshouldyoudo？（）
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？（）