We often use In-Built markup extensions such as Binding, Static Resource, Template Binding and Relative Source. We will use these markup extensions with curly braces {}. Now in Silverlight 5, we can also write our own Custom Markup Extensions.

Implementing custom markup extension:

1. Create a class, which should inherit from “MarkupExtension" or the class should implement the interface “IMarkUpExtension”. Class Name should end with “Extension”
2. “ImarkUpExtension” has a method “ProvideValue. Our Custom Markup Extension should implement this method. Return value of this method will be assigned to the property, for which custom markup extension has been binded.
3. We can pass parameters to this class by using public properties in class. We can also get the name of the control and property of control that has been binded by using “ServiceProvider”, which will be in default passed as parameter to “Provide Value” method.

Getting ControlName and Control Property, that Markup extensions is binded

  IProvideValueTarget ipValueTarget = serviceProvider.GetService(typeof(IProvideValueTarget)) as IProvideValueTarget;
  FrameworkElement targetElement = ipValueTarget.TargetObject as FrameworkElement;                   
  PropertyInfo vPropertyInfo = ipValueTarget.TargetProperty as PropertyInfo;
  // If it’s a dependency property,cast TargetProperty to dependency property instead of propertyinfo

Example:

public class CustomMarkupExtension :MarkupExtension
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public CustomMarkupExtension()
        {
        }        
        public override object ProvideValue(IServiceProvider serviceProvider)
        {            
            return Convert.ToString(FirstName + " "  + LastName);
        }        
    }

xmlns:local="clr-namespace:Sl5Features"
<TextBlock Text="{local:CustomMarkupExtension FirstName=Rami,LastName=Reddy}" />

• Reference 1  [24 clicks]
• Reference 2  [32134 clicks]
• Reference 3  [32134 clicks]

Category :	Controls Enhancements
Release :	All
Tags :	Silverlight 5,Controls,Custom Markup Extensions