Markup Extensions in WPF

In this article we are going to focus on Markup Extensions in WPF. They are used to extend capabilities of XAML(eXtensible Application Markup Language). the MarkupExtension class is present in the System.Xaml assembly.

the arguments can be passed either via constructor or properties.

Create a new WPF application and add a new class "RandomExtension" which must be inherited from the abstract class "MarkupExtension". Then implement this class by right clicking on the MarkupExtension class and selecting Implement Abstract class as shown below.

write the below code in the class which takes the values for from and to variables from the constructor. This class implements the ProvideValue method which is used to generate a random from between the from and to values provided by the user and then this new generated number is returned.

 public class RandomExtension : MarkupExtension
    {
       readonly int _from, _to;
       public RandomExtension(int from, int to)
       {
           _from = from;
           _to = to;

       }

       public RandomExtension(int to)
           : this(0, to)
       { }

       public static readonly Random _rnd = new Random();
        public override object ProvideValue(IServiceProvider serviceProvider)
        {
           //return a random number in the range provided by the constructors.
            return (double)_rnd.Next(_from, _to);
        }
    }

 <StackPanel>
        <TextBlock FontSize="{local:Random 10,100}" Text="Hello" x:Name="txt1"></TextBlock>
        <TextBlock Text="{Binding ElementName=txt1, Path=FontSize}"></TextBlock>
           </StackPanel>