MSDN Magazine - September 2008 - (Page 32)

Product Details and Binding Modes When an item in the ListBox has been selected, the code in the event handler fetches the selected Product from the ListBox’s SelectedItem and sets it to a Grid layout control’s DataContext. The Grid layout control is used as a container for the product details section, which contains a series of controls that allow the user to edit the selected product. Since the DataContext is inherited down the control tree, there is no need to set the DataContext on the individual TextBox and CheckBox controls. These controls all inherit the DataContext from their parent Grid control that was set in the lbProducts_SelectionChanged event handler. There are several TextBlock, TextBox, and CheckBox controls in the Grid layout control which contain binding declarations. A few snippets of XAML from this section are shown here: Figure 7 Three Binding Modes in Silverlight XAML Binding Mode Target is updated when Target is updated when source changes Source is updated when target changes OneTime Yes No No OneWay Yes Yes No TwoWay Yes Yes Yes Notice that the first snippet represents a TextBox that displays the UnitsInStock property from the Product source object. The second snippet shows the value of the Product instance’s CategoryName property. Note that the binding Mode property is set to TwoWay on the TextBox and it is set to OneWay (which is the default setting) on the TextBlock. The binding Mode property is a critical binding setting that determines how often and in which direction binding will occur between the target and its source. Figure 7 shows the three binding modes that can be used in Silverlight XAML and when they are updated. OneTime binding sends the source to the target when the application is started or the DataContext changes. OneWay binding sends the source to the target as well. However, if the source implements the INotifyPropertyChanged interface, the target will receive updates when the source is updated. TwoWay binding sends the source data to the target and if there are changes in the target property’s value, those will go back to the source. Both OneWay and TwoWay binding only notify the target about changes if the source Advanced Document Imaging Toolkits Zero-footprint Viewing, 3 Months of Free Gold Support, No Sweat. Features include Runtime Royalty-Free OCR, PDF annotations, ISIS support, CAD/CAM and WPF support, AJAX web image viewing with no plug-ins, and more—Take document and photographic imaging to the .NExT step. Visit Atalasoft.com for web demos, video tutorials, and a free trial. Atalasoft, Your .NET Imaging Partner Call us toll free at 866-568-0129 32 msdn magazine www.atalasoft.com Data Points http://www.atalasoft.com http://www.atalasoft.com

Table of Contents Feed for the Digital Edition of MSDN Magazine - September 2008

MSDN Magazine - September 2008 Contents Toolbox CLR Inside Out Data Points Advanced Basics Office Space Cutting Edge Hierarchy ID New Features for Microsoft SQL Server 2008 Prism Data Services Advanced WPF Test Run Security Briefs Foundations { End Bracket }

MSDN Magazine - September 2008

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