WPF TextBox MVVM DataBinding & use of UpdateSourceTrigger

If you are using a TextBox in your WPF application with MVVM pattern & want to keep the TextBox Text and the property in the ViewModel synchronized, you need to use UpdateSourceTrigger=PropertyChanged in the binding. Here is an example:

View XAML:
<Window x:Class="WPF.MainWindow" 
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
        Title="WPF TextBox MVVM DataBinding Example" Height="500" Width="500">
    <Grid>
        <TextBox Text="{Binding Path=Name, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" Height="25" />
    Grid>
Window>

View Code Behind:
using WPF.ViewModel;

namespace WPF
{
    public partial class MainWindow
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = new TextBoxViewModel();
        }
    }
}

ViewModel:
using System.ComponentModel;

namespace WPF.ViewModel
{
    public class TextBoxViewModel : INotifyPropertyChanged
    {
        private string _name;
        public string Name
        {
            get { return _name; }
            set
            {
                _name = value;
                OnPropertyChanged("Name");
            }
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;


        public void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }

        #endregion INotifyPropertyChanged Members
    }
} 


  

Comments

  1. ShadowJanuary 5, 2012 at 11:12 PM

    Hi,
    I'm doing the same way for binding,
    with a little difference,
    I want to check if the enter (\r\n) pressed or not, then do something and clear the textbox.
    so I changed the 'set' to:

    {
    _name = value;
    if (_name.IndexOf("\r\n") > -1)
    {
    dosomething();
    _name = "";
    }
    OnPropertyChanged("Name");
    }

    this works if I enter some text and then press enter,
    but if I press enter, the "\r\n" value remains in the textbox !
    any idea?

    ReplyDelete

Post a Comment

Popular posts from this blog

WPF How to Dispose ViewModel when the associated UserControl (Not Window) closes?

Note: If your WPF UserControl is hosted in MFC Window, you may want to clean-up the ViewModel that is DataContext of your UserControl. Since Unloaded event is not called reliably for the UserControl when the hosting MFC Window closes, there is a need for another solution. XAML: < UserControl  x : Class = "Views.MyUserControl"               xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation"               xmlns : x = "http://schemas.microsoft.com/winfx/2006/xaml"               xmlns : mc = "http://schemas.openxmlformats.org/markup-compatibility/2006"                 xmlns : d = "http://schemas.microsoft.com/expression/blend/2008"                 mc : Ignorable = "d"                 d : DesignHeight = "300"  d : DesignWidth = "300" >      < Grid >                   </ Grid > </ UserControl > Code Behind: using  System; using  ViewModels; name
Read more

C# How to unit test Dispatcher

Dispatcher provides services for managing the queue of work items for a thread. Sometimes to execute a task on a background thread.  Any task executed by calling Dispatcher.BeginInvoke(...) in unit test does not get executed until you do some wire-up. This is how you would unit test code with Dispatcher. using  System; using  System.Windows.Threading; using  Microsoft.VisualStudio.TestTools.UnitTesting; namespace  UnitTesting.Tests {     [ TestClass ]      public   class   DispatcherUtilTest     {          private   ClassThatUsesDispatcher  _subject;         [ TestInitialize ]          public   void  TestInitialize()         {             _subject =  new   ClassThatUsesDispatcher ();         }         [ TestMethod ]          public   void  UseDispatcher()         {              // Arrange              var  backgroundWorkDone =  false ;             _subject.BackgroungWorkAction = () => { backgroundWorkDone =  true ; };              // Act             _subject.DoWork(
Read more

WPF: How to Deep Copy WPF object (e.g. UIElement) ?

         ///  Generic Method to perform Deep-Copy of a WPF element (e.g. UIElement)          public   static  T DeepCopy (T element)         {              var  xaml =  XamlWriter .Save(element);              var  xamlString =  new   StringReader (xaml);              var  xmlTextReader =  new   XmlTextReader (xamlString);              var  deepCopyObject = (T) XamlReader .Load(xmlTextReader);              return  deepCopyObject;         }          ///  Test showing that the deep copied object does not have the same reference as the object being copied         [ TestMethod ]          public   void  DeepCopy()         {              // Arrange              Shape  shape =  new   Rectangle  {Fill =  new   SolidColorBrush ( Colors .Red)};              // Act              var  deepCopyShape =  MyClass .DeepCopy(shape);              // Assert              Assert .AreNotSame(shape, deepCopyShape);         }  
Read more