Data binding in Silverlight allows moving data between objects and UI controls. It extracts a property value from a source object and sets a property in a target object. The target property must be a dependency property. Data binding works with public source object properties and uses a binding expression to connect the source and target properties without specifying the source object. The data context provides a single source of data that can bind to multiple target elements. Target null values and fallback values provide default display values when the bound data is null. Data binding modes determine the data flow direction between source and target properties.

1. Data Binding in SilverlightMahenderSenior Software EngineerUnited Health Group

2. Mahender SarangamHaving close to 5 years of experience. Working as a Senior Software Engineer in United Health Group. Good Knowledge on C#, ASP.NET, Silverlight, WPF ,SQL Server, Team Foundation Server(TFS) and SharePoint Technology. MCTS Certified in Web Technologies.

3. Data Binding Data binding is a mechanism for moving the data from objects into UI controls.Data binding is a key in Silverlight that allows data shown on UI and then process changes. Data binding is a process that tells Silverlight to extract a property value from a source object and use it to set a property in a target object. Here Target Object which inherit from Dependency Object and its property must be a Dependency property.Data Binding works with Public properties of Source object. It does not work for fields.

4. Data BindingWe use Binding expression for binding Source property to Target property. Here we don’t mention source object which contain data. Generally in WPF/Silverlight, control uses Data context as Source Object or try to use source property of Binding expression.<UserControl.Resources><local:Product x:Key="resourceProduct"ModelNumber="AEFS100"ModelName="Portable Defibrillator" UnitCost="77"Description="Analyzes the electrical activity of a person's heart and appliesan electric shock if necessary."></local:Product></UserControl.Resources><TextBoxText="{Binding ModelNumber, Source={StaticResourceresourceProduct} }“></TextBox>

5. INotify Property ChangedThe INotifyPropertyChanged interface is a key part of the data binding infrastructure available in Silverlight. It contains a single event named PropertyChanged that is used to notify objects when a particular property value changes.

6. Data ContextData Context: The Data Context refers to a source of data that can be bound to a target. The Data Context often is set to an instance of an entityData Context is inherited to child elements and this makes it ideal for scenarios where you want to bind multiple elements to a single data source.Data Context is a property of Framework ElementWe use Binding expression for binding Source property to Target property

7. Target Null Value and Fall Back valuesTarget Null values are default values i.e. when bound data is NULL or there may be cases where value bounded is NULL. For example: <TextBox Text="{Binding ModelName, TargetNullValue='[No Model Name Set]' }"></TextBox>There might be cases , When Binding Properties to Target control ,binding throws exception or any binding operation failure , Fall back value provide a fall back value when binding is unable to return value<TextBox Text="{Binding ModelName, FallBackvalue='[No Model Name Set]' }"></TextBox>.String Format : Allows formatting of the bound value using standard formatting expressions. <TextBlock x:Name="CurrencyExample" Text="{Binding Cost, StringFormat=C}"></TextBlock> <TextBlock x:Name="BirthDateValueTextBlock" Text="{Binding BirthDate, StringFormat=MM/dd/yyyy}"></TextBlock>

8. Data Flow Each Binding expression has Mode property which determines how and when the data flows. There are 3 types of Data bindingOne Time Binding : Target property is set initially with the source data when the binding is createdOne way Binding : Update targets whenever source data changes. This is defaultTwo Way Binding : The target property is updated when the source property changes, and the source Property is updated when the target property changes.UpdateSourceTrigger : Silverlight supports only two values for Update SourceTrigger: Default and Explicit. It isn’t possible to choose PropertyChangedValidateonErrors and validate on exceptions

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