New binding feature of silverlight4beta (Part 2)

Dependencyobject supports binding

In versions earlier than silverlight4, only frameworkelement supports data binding. The following scenarios are not allowed:

<Canvas Width="100" Height="100"         RenderTransformOrigin="0.5, 0.5" Background="#FF2B6092">    <Canvas.RenderTransform>        <RotateTransform Angle="{Binding ElementName=slider, Path=Value}" />    </Canvas.RenderTransform></Canvas><Slider x:Name="slider" Height="20" Margin="0,225,0,55" Minimum="0"         Maximum="360" />

Rotatetransform is certainly not a frameworkelement, and this scenario is so classic. Sl4 makes us ready

Supports string index binding.

Sl4beta supports binding collection items through string indexes. This means that we can easily bind a dictionary object or a set of custom types that provide string indexes.

For example, define an object class:

public class Employee : INotifyPropertyChanged {    private Dictionary<string, Object> _customProps;    public Dictionary<string, Object> CustomProperties {        get {            if (_customProps == null)                _customProps = new Dictionary<string, object>();            return _customProps;        }    }}

Set Data Context

var emp = new Employee() { FirstName = "John" };emp.CustomProperties.Add("Nickname", "Johnny");this.DataContext = emp;

Bind by string Index

<TextBox Text="{Binding Path=CustomProperties[Nickname]}"/>

New constructor of observablecollection

Observablecollection is very powerful (but it seems to be too long). It is a common operation to convert list <t> to observablecollection <t> and then bind it. In sl4, we can simplify this process through an overload of the constructor of observablecollection.

List<string> ColorList = new List<string> { "red", "blue", "yellow" };var ColorOC = new ObservableCollection<string>(ColorList);

In additionIdataerrorinfoAndInotifydataerrorinfoThese two new verification-related interfaces are to be described separately in an article.

OK, have fun ~