You are creating a Windows Forms application by using the .NET Framework 3.5  The application requires a form to display a clock.You need to create a circular form to display the clock. Which code segment should you use？（）

YouarecreatingaWindowsapplicationbyusingthe.NETFramewor...

单项选择题

You are creating a Windows application by using the .NET Framework 3.5.You create an instance of the BackgroundWorker component named backgroundWorker1 to asynchronously process timeconsuming reports in the application.You write the following code segment in the application （Line numbers are included for reference only.）

You need to write a code segment that reports to the application when the background process detects any of the following actions：  
（1）An exception is thrown  
（2）The process is cancelled  
（3）The process is successfully completed   
Which code segment should you insert？（）

You are creating a Windows application by using the .NE...

单项选择题

You are creating a Windows application by using the .NET Framework 3.5.You plan to create a form that might result in a timeconsuming operation.You use the QueueUserWorkItem method and a Label control named lblResult.You need to update the users by using the lblResult control when the process has completed the operation. Which code segment should you use？（）

You are creating a Windows Forms application for a cour...

单项选择题

You are creating a Windows Forms application for a courier company by using the .NET Framework 3.5.You create a form that allows customers to track the progress of their shipments.The form contains the following elements： 
（1）A text box named txtTN that allows users to enter a tracking number. 
（2）An ErrorProvider control named ErrorProvider1 that informs users of an invalid tracking number. 
（3）A function named ValidTrackingNumber that validates tracking numbers.  
You need to ensure that the txtTN text box is validated.  
Which code segment should you use？（）