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？（）

A.Create a new custom class for the control that is derived from the Control class.
B.Create a new custom class for the control that is derived from the UserControl class.
C.Create a new custom class for the control that is derived from the ContentControl class.
D.Create a new custom class for the control that is derived from the ContentPresenter class.

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？（）

A.Extend the Control class.
B.Extend the ContainerControl class.
C.Create protected accesses for each control property.
D.Create public accesses for the properties of the BindingSource control.

单项选择题YouarecreatingaWindowsFormsapplicationbyusingthe.NetFramework3.5Youplantodisplaydetailedhelpinstructionsforeachcontrolintheform.Youcreateahelpfile.YouconfigureaHelpProvidercomponentontheform.YouneedtodisplaythehelpfileforthecontrolthatisfocusedwhentheF1keyispressed.WhichmethodoftheHelpProviderclassshouldyoucallforeachcontrol？（）

A.SetShowHelp
B.SetHelpString
C.SetHelpKeyword
D.SetHelpNavigator

多项选择题YouaredevelopingaWindowsFormsApplicationbyusingthe.NETFramework3.5.YouplantocreateacustomizedPrintPreviewdialogboxintheapplication.Youneedtoensurethatuserscanpreviewtheirdocumentsbeforeprinting.Whichtwoactionsshouldyouperform？（）

A.Add a PrintPreviewDialog control to the form.
B.Add a PrintPreviewControl control to the form.
C.Create and initialize a PrintDocument object on the form and then implement the PrintPage event handler.
D.Create and initialize a PrintDocument object on the form and then implement the BeginPrint event handler.
E.Set the Document property of the PrintPreviewDialog control to the PrintDocument instance that must be printed.

单项选择题YouaredevelopingaWindowsFormsApplicationbyusingthe.NETFramework3.5.Youplantodesignacompositecustomcontrolfortheapplication.YouincludeaListBoxcontrolhasapropertythatprovidestheitemcountoftheListBoxcontrol.Youneedtoensurethatthepropertycannotbeaccessedatdesigntime.Whichattributeshouldyouuse？（）

A.[Bindable（false）]
B.[DesignOnly（false）]
C.[EditorBrowsable（EditorBrowsableState.Never）]
D.[Browsable（false）]