单项选择题
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.
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？（）
单项选择题 You are creating a Windows Forms Application by using the .NET Framework 3.5.You plan to design a control for the application.You need to ensure that the control meets the following requirements： （1）Contains the DataGridView， BindingSource， and BindingNavigator controls. （2）Exposes the properties of the BindingSource control. （3）Protects the properties of the DataGridView and BindingNavigator controls. What sholud you do？（）
单项选择题 YouarecreatingaWindowsFormsapplicationbyusingthe.NetFramework3.5Youplantodisplaydetailedhelpinstructionsforeachcontrolintheform.Youcreateahelpfile.YouconfigureaHelpProvidercomponentontheform.YouneedtodisplaythehelpfileforthecontrolthatisfocusedwhentheF1keyispressed.WhichmethodoftheHelpProviderclassshouldyoucallforeachcontrol？（）