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"           ...
Read more

WPF: VisualTreeHelper Find Parent of Specific Type

While working with WPF Visual Tree, one of the common tasks is to find the Parent(Ancestor) or Child of any specific element (DependencyObject). The following piece of code traverses the visual tree recursively and finds the type of parent you are looking for related to the element you pass in. For example: If the Visual Tree hierarchy is like this: Grid StackPanel ListBox You can call the function like this to find the Grid: FindAncestor (( DependencyObject )ListBox) ; public   static  T FindAncestor ( DependencyObject  dependencyObject)              where  T :  DependencyObject         {              var  parent =  VisualTreeHelper .GetParent(dependencyObject);              if  (pare...
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...
Read more