Validating domain objects

A modeless dialog box at least provides a Close button to close the dialog box, and may provide additional buttons to execute specific functions, such as a Find Next button to find the next word that matches the find criteria of a word search.Windows Presentation Foundation (WPF) allows you to create several types of dialog boxes, including message boxes, common dialog boxes, and custom dialog boxes.Show(message Box Text, caption, button, icon) ' Process message box results Select Case result Case Message Box Result. Windows implements a variety of reusable dialog boxes that are common to all applications, including dialog boxes for opening files, saving files, and printing. Filter = "Text documents (.txt)|*.txt"; // Filter files by extension // Show open file dialog box Nullable' Configure open file dialog box Dim dlg As New Microsoft. Default Ext = ".txt" ' Default file extension dlg. Filter = "Text documents (.txt)|*.txt" ' Filter files by extension ' Show save file dialog box Dim result? Show Dialog() ' Process save file dialog box results If result = True Then ' Save document Dim filename As String = dlg. The print dialog box, shown in the following figure, is used by printing functionality to choose and configure the printer that a user would like to print data to. The following code shows how to create, configure, and show one. Here, the code is passing default information (the current margins) to the dialog box. Owner property with a reference to the window that is showing the dialog box.Since these dialog boxes are implemented by the operating system, they can be shared among all the applications that run on the operating system, which helps user experience consistency; when users are familiar with the use of an operating system-provided dialog box in one application, they don't need to learn how to use that dialog box in other applications. Filter = "Text documents (.txt)|*.txt" ' Filter files by extension ' Show open file dialog box Dim result? Show Dialog() ' Process open file dialog box results If result = True Then ' Open document Dim filename As String = dlg. File Name End If For more information on the save file dialog box, see Microsoft. The common print dialog box is implemented as the Print Dialog class, and is located in the System. In general, you should always set the owner for a dialog box to provide window state-related behaviors that are common to all dialog boxes (see WPF Windows Overview for more information). Max Margin) Return New Validation Result(False, msg) End If ' Number is valid Return New Validation Result(True, Nothing) End Function End Class End Namespace In this code, the validation logic of a validation rule is implemented by overriding the Validate method, which validates the data and returns an appropriate Validation Result.Warning; ' Configure the message box to be displayed Dim message Box Text As String = "Do you want to save changes? End Select For more information on using message boxes, see Message Box, Message Box Sample, and Dialog Box Sample. When a menu item runs a function that displays a dialog box which does not require user interaction, such as an About dialog box, an ellipsis is not required." Dim caption As String = "Word Processor" Dim button As Message Box Button = Message Box Button. Although Message Box may offer a simple dialog box user experience, the advantage of using Message Box is that is the only type of window that can be shown by applications that run within a partial trust security sandbox (see Security), such as XAML browser applications (XBAPs). A dialog box is typically shown as a result of a user selecting a menu item to perform a domain-specific function, such as setting the margins of a document in a word processor.

Pressing the Cancel button indicates that a user wants to stop the function from executing altogether.This is good behavior for a dialog box; a user should be able to freely navigate the controls in a dialog box whether or not data is valid.However, this means a user can enter invalid data and press the OK button."; string caption = "Word Processor"; Message Box Button button = Message Box Button. This topic shows how to use Window to create a typical modal dialog box implementation, using the The user experience for a dialog box also extends into the menu bar of the window that opens the dialog box.Yes No Cancel; Message Box Image icon = Message Box Image. When a menu item runs a function that requires user interaction through a dialog box before the function can continue, the menu item for the function will have an ellipsis in its header, as shown here.

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The following figure shows a message box that displays textual information, asks a question, and provides the user with three buttons to answer the question. While common dialog boxes are useful, and should be used when possible, they do not support the requirements of domain-specific dialog boxes.

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