My name is Edward Tanguay. I'm an American software and web developer living and working in Berlin, Germany.
WPF CODE EXAMPLE created on Sunday, April 18, 2010 permalink
An UpdateSourceTrigger workaround for Silverlight
Although WPF has UpdateSourceTrigger and Silverlight doesn't, you can emulate this functionality with this workaround from Thomas Huber. When you type in the TextBox, your text is immediately appears transformed in the TextBlock below.
XAML:
<UserControl x:Class="TestUpdate123.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:TestUpdate123"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480">
    <StackPanel Margin="10" HorizontalAlignment="Left">

            <TextBox
        Text="{Binding InputText, Mode=TwoWay}"
        local:BindingHelper.UpdateSourceOnChange="True"
        Height="200"
        Width="600"
        AcceptsReturn="True"
        Margin="0 0 0 10"/>

        <TextBlock
            Text="{Binding OutputText}"/>

        </StackPanel>
</UserControl>

Code Behind:
using System.Windows;
using System.Windows.Controls;
using System.ComponentModel;
using System.Collections.Generic;

namespace TestUpdate123
{
    public partial class MainPage : UserControl, INotifyPropertyChanged
    {

        #region ViewModelProperty: InputText
        private string _inputText;
        public string InputText
        {
            get
            {
                return _inputText;
            }

            set
            {
                _inputText = value;
                OnPropertyChanged("InputText");
                UpdateOutputText();
            }
        }
        #endregion .

        #region ViewModelProperty: OutputText
        private string _outputText;
        public string OutputText
        {
            get
            {
                return _outputText;
            }

            set
            {
                _outputText = value;
                OnPropertyChanged("OutputText");
            }
        }
        #endregion .

        public MainPage()
        {
            InitializeComponent();
            DataContext = this;
            InputText = "default text";
            UpdateOutputText();
        }

        void UpdateOutputText()
        {
            OutputText = InputText.Replace(" ", "_");
        }

        #region INotifiedProperty Block
        public event PropertyChangedEventHandler PropertyChanged;

        protected void OnPropertyChanged(string propertyName)
        {
            PropertyChangedEventHandler handler = PropertyChanged;

            if (handler != null)
            {
                handler(this, new PropertyChangedEventArgs(propertyName));
            }
        }
        #endregion .
    }
}
need markup?