Friday, June 3, 2016

WPF Binding


Data binding is the mechanism to flow the Data from source to target and vice versa. This mechanism provide a way to update the user interface when there is change in data in ViewModel side.

A 'Binding' can only be set on a DependencyProperty of a DependencyObject

Data binding can be Unidirectional or Bidirectional.

Binding work along with Notification mechanism on both side.

.Net Property: in this side, use INotifyPropertyChanged interface to raise the PropertyChanged event.
Dependency Property:  In this side, PropertyChanged callback of the property metadata is in Action.

Binding Mode

Binding mode describes the direction of the data flow in a binding.


The default value varies for each dependency property. In general, user-editable control properties, such as those of text boxes and check boxes, default to two-way bindings, whereas most other properties default to one-way bindings

OneTime :Update the binding target when the application start or when the data context change.

OneWay :Update the biding target from source not vice versa.

OneWayToSource Update the source from binding target not vice versa.

TwoWay : This binding to ensure data synchronization between source and target, when any change in source reflect in target and any change in target reflect in source.

In XAML {Binding} mark up extension is use for Data Binding.

<Label Content=”Binding [.Net Property of ViewModel]” />
e.g.  FirstName is the property in the View Model and want to bind with Lable
<Label Content=”Binding FirstName” /> 

Markup Extension

Common markup extension specific to WPF only.

  1. StaticResource
  2. DynamicResource
  3. Binding
  4. RelativeSource
  5. TempletBinding
  6. ColorConvertedBitmap
  7. ComponentResourceKey
  8. ThemeDictionary

Some Terminology

Source: View Model Property (.Net property)
Target: UI (XAML) DP property

...In progress