You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. 
You write the following code segment. (Line numbers are included for reference only.)

The TextBox control is data-bound to an instance of the Contact class.  
You need to ensure that the Contact class contains a business rule to ensure that the ContactName property is not empty or NULL.
You also need to ensure that the TextBox control validates the input data. 
Which two actions should you perform?（）

多项选择题You use Microsoft .NET Framework 4 to create a Windows Forms application. You add a new class named Customer to the application. You select the Customer class to create a new object data source. You add the following components to a Windows Form: A BindingSource component named customerBindingSource that is data-bound to the Customer object data source. A set of TextBox controls to display and edit the Customer object properties. Each TextBox control is data-bound to a property of the customerBindingSource component. An ErrorProvider component named errorProvider that validates the input values for each TextBox control. You need to ensure that the input data for each TextBox control is automatically validated by using the ErrorProvider component. Which two actions should you perform?（）

A. Implement the validation rules inside the Validating event handler of each TextBox control by throwing an exception when the value is invalid.
B. Implement the validation rules inside the TextChanged event handler of each TextBox control by throwing an exception when the value is invalid.
C. Implement the validation rules inside the setter of each property of the Customer class by throwing an exception when the value is invalid.
D. Add the following code segment to the InitializeComponent method of the Windows Form.   this.errorProvider.DataSource = this.customerBindingSource;
E. Add the following code segment to the InitializeComponent method of the Windows Form.    this.errorProvider.DataSource = this.customerBindingSource.DataSource;    this.errorProvider.DataMember = this.customerBindingSource.DataMember;

单项选择题You use Microsoft Visual Studio 2010 and Microsoft . NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You create a WPF window in the application. You add the following code segment to the application. The DataContext property of the window is set to an instance of the ViewModel class. The Data property of the ViewModel instance is initialized with a collection of BusinessObject objects. You add a TextBox control to the Window. You need to bind the Text property of the TextBox control to the Name property of the current item of the CollectionView of the DataContext object. You also need to ensure that when a binding error occurs, the Text property of the TextBox control is set to N A . Which binding expression should you use?（）

A. { Binding Path=Data/Name, FallbackValue='N/A' }
B. { Binding Path=Data.Name, FallbackValue='N/A' }
C. { Binding Path=Data/Name, TargetNullValue='N/A' } 
D. { Binding Path=Data.Name, TargetNullValue='N/A' }

单项选择题You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You write the following code fragment. You need to ensure that the ButtonHandler method is not executed when the user clicks the CancelButton button. Which code segment should you add to the code-behind file?（）

A.
B.
C.
D.

单项选择题You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You want to add an audio player that plays .wav or .mp3 files when the user clicks a button. You plan to store the name of the file to a variable named SoundFilePath. You need to ensure that when a user clicks the button, the file provided by SoundFilePath plays. What should you do?（）

A. Write the following code segment in the button onclick event.     System.Media.    SoundPlayer player = new System.Media.    SoundPlayer(SoundFilePath); player.play();
B. Write the following code segment in the button onclick event.    MediaPlayer player = new MediaPlayer();     player.Open(new URI(SoundFilePath),    UriKind.Relative)); player.play();
C. Use the following code segment from the PlaySound()    Win32 API function and call the PlaySound function in the button onclick event.    [sysimport(dll="winmm.dll")]     public static extern long PlaySound(String SoundFilePath, long hModule, long dwFlags);
D. Reference the Microsoft.DirectX Dynamic Link Libraries.     Use the following code segment in the button onclick event.     Audio song = new Song(SoundFilePath);     song.CurrentPosition = song.Duration; song.Play();

单项选择题You create a Windows client application by using Windows Presentation Foundation (WPF). The application contains the following code fragment. You need to assign lbDetails to use the detail data template when btnDetails is clicked. Which code segment should you write for the click event handler for btnDetails?（）

A. lbDetails.ItemsPanel.FindName("detail",lbDetails);
B. var tmpl = (ControlTemplate)FindResource("detail");    lbDetails.Template = tmpl; 
C. var tmpl = (DataTemplate)FindName("detail");    lbDetails.ItemTemplate = tmpl;
D. var tmpl = (DataTemplate)FindResource("detail");    lbDetails.ItemTemplate=tmpl;