Unwantend checkbox/datasource behavior, content reloads on checkbox.Checked event

Question

I have a form with a textbox, a checkbox and a button. TextBox and Button are bound to an xml file via an XmlDataProvider defined in the Grid.Datacontext. The Text of the textbox.Text is changed on button click.

Here comes the problem: when i check/uncheck the checkbox the TextBox.Text property resets to the value from the XmlDataProvider.

How can i prevent the checkbox box from reloading the data from my DataProvider? Why does my checkbox behave this way?

This behavior also applies for other controls like ComboBox, DataPicker and RadioButton

I created a simply example to illustrate the problem:

MainWindow.xaml:

<Window x:Class="submitbehavior.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="150" Width="250">
    <Grid>
        <Grid.DataContext>
            <XmlDataProvider x:Name="DataProvider" XPath="/" Source="datacontext.xml"/>
        </Grid.DataContext>
        <StackPanel>
            <TextBox Name="MyTextBox" Text="{Binding XPath=/Contact/Lastname}" Width="100" Height="30" VerticalAlignment="Top" HorizontalAlignment="Left"/>
            <CheckBox IsChecked="{Binding XPath=/Contact/@ShowsInterest}" Width="100" Height="30" VerticalAlignment="Top" HorizontalAlignment="Left" VerticalContentAlignment="Center" />
            <Button Content="Click" Click="ButtonBase_OnClick" Height="30" />
        </StackPanel>
    </Grid>
</Window>

MainWindow.xaml.cs

using System.Windows;

namespace submitbehavior
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void ButtonBase_OnClick(object sender, RoutedEventArgs e)
        {
            this.MyTextBox.Text = "test";
        }
    }
}

Datasource (datecontext.xml):

<Contact ShowsInterest="true">
  <Name>John</Name>
  <Lastname>Doe</Lastname>
</Contact>

Answer 1

TextBox Text property binding will update the binding source on lost focus. Update your binding to:

    <TextBox Name="MyTextBox" Text="{Binding XPath=/Contact/Lastname, UpdateSourceTrigger=PropertyChanged}" Width="100" Height="30" VerticalAlignment="Top" HorizontalAlignment="Left"/>