单项选择题
You create an isntance of a BackgroundWorker Component named backgroundworker1.You discover that when the application attempts to cancel the background process you get an exception from the following code segment：
backgroundworker1.CancelAsync（）；
You need to configure the BackgroundWorker component appropriately to prevent to application from exception.What should you do？（）
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
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单项选择题
YouarecreatingaWindowsFormsapplicationbyusingthe.NetFramework3.5.Youplantodesignacompositecontrolfortheapplication.Youneedtoderivethecontrolfromabaseclassthatsupportstemplates.Whatshouldyoudo？（）
A.Derive from the Control class.
B.Derive from the UserControl class.
C.Derive from the ScrollableControl class.
D.Derive from the ContainerControl class. -
单项选择题
YouarecreatingaWindowsFormsApplicationbyusingthe.NETFramework3.5.Usersusetheapplicationtoprocessandapproveinvoices.AlistofrecentlyaccessedinvoicesisstoredintheuserssettingssectionoftheApp.configfile.Youneedtomaintainthelistofinvoicesfromthelastpersistedstate.Whatshouldyoudo？（）
A.Use the Properties.Settings object during runtime.
B.Use the Properties.Settings.Default object during runtime.
C.Use the ConfigurationManager.AppSettings object during runtime.
D.Use the ConfigurationManager.GetSection method during runtime. -
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？（）
A.Set the Result property of the DoWorkEventArgs instance to True before you attempt to report the progress.
B.Set the CancellationPending property of backgroundWorker1 to True before you attempt to report the background process
C.Set the WorkerReportsProgress property of backgroundWorker1 to True before you attempt to report the background process.
D.Report the progress of the background process in the backgroundWorker1_ProgressChanged event.
