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WPF pass ListView selected items to another ListView

I have a list view with some items in the main window. Then I add checked boxes so that when an item is selected it also get checked.
Now I tried to pass the selected items from that list view to another list view but here is what I get:
Here is my XAML:
<Window x:Class="WpfApp1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApp1"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Canvas HorizontalAlignment="Left" Height="299" Margin="10,10,0,0" VerticalAlignment="Top" Width="497">
<TabControl Height="279" Canvas.Left="10" Canvas.Top="10" Width="477">
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5">
<ListView Name="lv1" Margin="0,0,0,0" HorizontalAlignment="Left" VerticalAlignment="Top" Height="110" Width="471">
<ListViewItem>
<CheckBox >
<StackPanel Orientation="Horizontal">
<TextBlock Text="Apple"/>
</StackPanel>
</CheckBox>
</ListViewItem>
<ListViewItem>
<CheckBox >
<StackPanel Orientation="Horizontal">
<TextBlock Text="Orange"/>
</StackPanel>
</CheckBox>
</ListViewItem>
</ListView>
<Button Content="Copy" Width="100" Height="25" Click="Button_Click"/>
<ListView Name="lv2" HorizontalAlignment="Left" VerticalAlignment="Bottom" Height="110" Width="471"/>
</Grid>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
<TabItem Header="TabItem">
<Grid Background="#FFE5E5E5"/>
</TabItem>
</TabControl>
</Canvas>
</Grid>
Here is code behind in c#:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
namespace WpfApp1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
List<string> lv1list = new List<string>();
foreach (var i in lv1.SelectedItems)
{
lv1list.Add(i.ToString());
}
lv2.Items.Add(lv1.SelectedItems);
}
}
}
What went wrong here?

The problem is you're adding a complete list as an item which is why you're getting the (Collection) value.
What you can do is get all the selected item in a list them loop and add them one by one
private void Button_Click(object sender, RoutedEventArgs e)
{
var selectedItems = lv1.SelectedItems;
for(int i = 0; i < selectedItems.Count; i++)
{
lv2.Items.Add(selectedItems[i]);
}
}
You might also want to clear your lv2 before adding the new values
lv2.Items.Clear();
Another option which wouldn't require you to press a button so that the values appear in the second listview would be to bind the ItemsSource of your lv2 to the SelectedItems of your lv1
lv2.ItemsSource = lv1.SelectedItems;
You can do that once at the beginning and lv2 will always contain the selected items of lv1 and will update as soon as the selected items changes.

I made some more modifications and then I realized it is not working as it should. I have a "foreach statement" looping through all the checked/selected items in listBox1, then inside the "foreach statement" there is an "If statement" to check if the checked/selected items from listBox1 are not in listBox2, if they aren't then they are copied to listBox2. Each condition of the "If statement" should display relevant MessageBox. The problem now is that the "If statement" doesn't work properly. I know this, because I cannot see the correct relevant MessageBox to the correct condition of the "If statement". However the items are not duplicated, meaning they are not being copied over and over only they appear duplicated in the MessageBox. Here is my code and hope someone can spot my mistake
using System.Windows;
using System.Windows.Controls;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows.Controls.Primitives;
using System.Windows.Media;
using System;
namespace MYNAMESPACE
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : INotifyPropertyChanged
{
public MainWindow()
{
InitializeComponent();
// To initialise the List and use it outside the class
//MyListItem instanceOfClass = new MyListItem();
//List<CheckBoxListItem> listOfItems = instanceOfClass.MyMethod();
//listBox1.ItemsSource = listOfItems;
}
public class CheckBoxListItem : INotifyPropertyChanged
{
public bool CheckStatus { get; set; }
public string Text { get; set; }
public CheckBoxListItem(bool _CheckStatus, string _Text)
{
CheckStatus = _CheckStatus;
Text = _Text;
}
public event PropertyChangedEventHandler PropertyChanged;
}
public class MyListItem
{
public List<CheckBoxListItem> MyMethod()
{
List<CheckBoxListItem> items = new List<CheckBoxListItem>();
items.Add(new CheckBoxListItem(false, "Item 1"));
items.Add(new CheckBoxListItem(false, "Item 2"));
items.Add(new CheckBoxListItem(false, "Item 3"));
return items;
}
}
public List<string> selectedNames = new List<string>();
private void CheckBox_Click(object sender, RoutedEventArgs e)
{
var checkBox = sender as CheckBox;
var item = checkBox.Content;
bool isChecked = checkBox.IsChecked.HasValue ? checkBox.IsChecked.Value : false;
if (isChecked)
selectedNames.Add(item.ToString());
else
selectedNames.Remove(item.ToString());
}
public string selections;
bool updatedItems;
public void Button_Click(object sender, RoutedEventArgs e)
{
foreach (string selection in selectedNames)
{
selections += selection + Environment.NewLine;
if (!listBox2.Items.Contains(selection))
{
listBox2.Items.Add(selection);
updatedItems = true;
}
else if (listBox2.Items.Contains(selection))
{
updatedItems = false;
}
}
if (updatedItems == true)
MessageBox.Show("Add items are: " + selections);
else if (updatedItems == false)
MessageBox.Show("No update to selection was made.");
}
private void CheckStatus(string propName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));
}
public event PropertyChangedEventHandler PropertyChanged;
}
}

WPF binding controls

I've just started learning WPF desktop application. I've written some let say easy code below, to excercise binding operation.
The problem is:
I wanted type sth in TextBox and see it simultaneously in TextBlock, but after compiling and running app, controls on form do not behave as I described.
Can anybody help me to fix it?
MainWindow.xaml:
<Window x:Class="Napisy.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:Napisy"
xmlns:mv="clr-namespace:Napisy.ModelWidoku"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<mv:NapisyModelWidoku x:Key="napisyModelWidoku"/>
</Window.Resources>
<Grid DataContext="{StaticResource napisyModelWidoku}">
<Grid.RowDefinitions>
<RowDefinition Height="1*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="1*"/>
</Grid.RowDefinitions>
<TextBox Grid.Row="1" Margin="10,10,10,10" Text="{Binding Path=Tekst,Mode=TwoWay}"/>
<TextBlock Grid.Row="2" Margin="10,10,10,10" Text="{Binding Path=Wyswietl,Mode=OneWay}"/>
</Grid>
</Window>
ViewModel code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Napisy.Model;
using System.ComponentModel;
namespace Napisy.ModelWidoku
{
public class NapisyModelWidoku : INotifyPropertyChanged
{
NapisyModel model = new NapisyModel();
public string Tekst
{
get
{
return model.Tekst;
}
set
{
model.Tekst = value;
OnPropertyChanged(nameof(Tekst));
OnPropertyChanged(nameof(Wyswietl));
}
}
public string Wyswietl
{
get
{
return model.Tekst;
}
}
public event PropertyChangedEventHandler PropertyChanged;
void OnPropertyChanged(string nazwa)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nazwa));
}
}
}
Model Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Napisy.Model
{
public class NapisyModel
{
public string Tekst { get; set; }
}
}
EDIT:
Problem description,
before class NapisyModelWidoku, acces modificator public added,
added OnPropertyChanged(nameof(Tekst));
instead OnPropertyChanged("Wyswietl"); used OnPropertyChanged(nameof(Wyswietl));
After typing text into TextBox still TextBlock not refresh automatically. Still hope I receive tips. Thanks

Along with adding UpdateSourceTrigger in both bindings, make below change also,
public string Tekst
{
get
{
return model.Tekst;
}
set
{
model.Tekst = value;
OnPropertyChanged("Tekst");
OnPropertyChanged("Wyswietl");
}
}

I ran your code and it does not work because PropertyChanged is null. You have to set the datacontext of your view so that the PropertyChangedEventHandler can be binded.
Add in your code behind, i-e MainWindow.xaml.cs
public MainWindow()
{
InitializeComponent();
this.DataContext = new NapisyModelWidoku();
}

WPF databinding cannot get data

I am writting a login window using WPF and C#,but got stuck when I attempted to retrive username from the TextBox.The class property which I bind to the TextBox always get a null value,and I cannot figure out why.
MainWindow.xaml
<Window x:Class="Databinding.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="256*"/>
<ColumnDefinition Width="261*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Label Grid.Row="0" Grid.Column="0" Content="Username" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" HorizontalContentAlignment="Right" VerticalContentAlignment="Center" FontSize="20"/>
<Label Grid.Row="1" Grid.Column="0" Content="Password" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" HorizontalContentAlignment="Right" VerticalContentAlignment="Center" FontSize="20"/>
<Button Content="Confirm" Click="Confirm_Click" IsDefault="True" Grid.Row="2" Grid.Column="0" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" FontSize="20"/>
<Button Content="Cancel" Click="Cancel_Click" IsCancel="True" Grid.Row="2" Grid.Column="1" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" FontSize="20"/>
<TextBox x:Name="TextUsername" Grid.Row="0" Grid.Column="1" HorizontalAlignment="Stretch" Margin="0,0,0,0" TextWrapping="Wrap" VerticalAlignment="Stretch" ToolTip="Enter your username"/>
<PasswordBox x:Name="Password" Grid.Row="1" Grid.Column="1" HorizontalAlignment="Stretch" Margin="0,0,0,0" VerticalAlignment="Stretch" ToolTip="Enter your password"/>
</Grid>
MainWindow.xaml.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;
namespace Databinding
{
/// <summary>
/// MainWindow.xaml 的交互逻辑
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Confirm_Click(object sender, RoutedEventArgs e)
{
Login LoginInfo = new Login();
Binding bindingLogin = new Binding();
bindingLogin.Source = LoginInfo;
bindingLogin.Path = new PropertyPath("Username");
bindingLogin.Mode = BindingMode.TwoWay;
bindingLogin.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
BindingOperations.SetBinding(this.TextUsername, TextBox.TextProperty, bindingLogin);
if(LoginInfo.Username=="admin" && this.Password.Password=="admin")
{
MessageBox.Show("Welcome!","Login Status");
}
else
{
MessageBox.Show("Something is wrong!","Login Status");
}
}
private void Cancel_Click(object sender, RoutedEventArgs e)
{
this.Close();
}
}
public class Login:INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string username;
public string Username
{
get
{
return username;
}
set
{
username = value;
if(this.PropertyChanged!=null)
{
this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs("Username"));
}
}
}
}
}
I know databinding is not a wise option in this case,and I can get things done more efficently by just using
string Username = this.TextUsername.Text
Anyway,this is a some demo,and I have to use databinding in my project.What's wrong with my code？

At the point you attach your binding, Login.Username is null, and since the binding is two way WPF will update your textbox to null to match.
Bindings are supposed to be active all the time, and declared in the XAML, rather than bound at the point you want data. You are defeating the object of using bindings. Like you say, it would be far easier to just grab the text directly if you are going to do it explicitly.

The problem is when user entering/changing Text in the TextUsername, your binding is not there yet, (your binding will only be there after the Confirm_Click, and will be reset with each Confirm_Click) so you need to move it to the constructor.
namespace Databinding
{
public partial class MainWindow : Window
{
Login LoginInfo;
public MainWindow()
{
InitializeComponent();
LoginInfo = new Login();
Binding bindingLogin = new Binding();
bindingLogin.Source = LoginInfo;
bindingLogin.Path = new PropertyPath("Username");
bindingLogin.Mode = BindingMode.TwoWay;
bindingLogin.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
BindingOperations.SetBinding(this.TextUsername, TextBox.TextProperty, bindingLogin);
}
//... rest
}
}
And you could easily apply the binding in XAML, and avoid all of these code behind if you can set the DataContext of your window correctly e.g.:
<TextBox x:Name="TextUsername" Text="{Binding Username}" ..../>

The below code will works, not sure if it's a good practice thou:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.ComponentModel;
namespace Databinding
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
Login LoginInfo;
Binding bindingLogin;
public MainWindow()
{
InitializeComponent();
LoginInfo = new Login();
bindingLogin = new Binding();
bindingLogin.Source = LoginInfo;
bindingLogin.Path = new PropertyPath("Username");
bindingLogin.Mode = BindingMode.TwoWay;
bindingLogin.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged;
}
private void Confirm_Click(object sender, RoutedEventArgs e)
{
BindingOperations.SetBinding(this.TextUsername, TextBox.TextProperty, bindingLogin);
if(LoginInfo.Username=="admin" && this.Password.Password=="admin")
{
MessageBox.Show("Welcome!","Login Status");
}
else
{
MessageBox.Show("Something is wrong!","Login Status");
}
}
private void Cancel_Click(object sender, RoutedEventArgs e)
{
this.Close();
}
}
public class Login:INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private string username;
public string Username
{
get
{
return username;
}
set
{
username = value;
if(this.PropertyChanged!=null)
{
this.PropertyChanged.Invoke(this, new PropertyChangedEventArgs("Username"));
}
}
}
}
}

Freezing main window after adding some items from childwindow

I am working on Silverlight 4 with mvvm and WCF services.
Whenever I am adding items from child window to main window. But at the same time main window automatically going to disabling mode. I think main window automatically freezes.
ChildWindow ViewModel
public class AddFormFieldInformationViewModel : ViewModelBase
{
private FieldInformationViewModel _FieldInformationViewModel;
public FieldInformationViewModel FieldInformationViewModel
{
get { return _FieldInformationViewModel; }
set
{
_FieldInformationViewModel = value;
RaisePropertyChanged("FieldInformationViewModel");
}
}
public void MoveSave(object obj)
{ this.FieldInformationViewModel.SelectedFormFields = FieldInformationModel;
ResultHandler(true);
}
public Action ResultHandler { get; set; }
}
ChildWindow .xaml.cs file
public partial class AddExistingFormFieldCategoryView : ChildWindow
{
private AddFormFieldInformationViewModel vm;
public AddExistingFormFieldCategoryView()
{
InitializeComponent();
vm = new AddFormFieldInformationViewModel();
this.DataContext = vm;
vm.ResultHandler = result => { if (result) { Close(); } };
}
}
Main Window ViewModel
public class FieldInformationViewModel : ViewModelBase
{ private void executeOpenChildWindow(object parameter)
{
AddExistingFormFieldCategoryView cw = new AddExistingFormFieldCategoryView();
((AddFormFieldInformationViewModel)cw.DataContext).FieldInformationViewModel = this;
cw.Show();
}
}
After adding items from child window into main window, sometimes my main window is automatically freezing.

Hi this is a bug you are experiencing see the sample below. I the same issue and you have to manually enable the display of the main page:
private static void ShowError(string message, string details)
{
ErrorWindow error = new ErrorWindow(message, details);
error.Closed += new EventHandler(error_Closed);
error.Show();
}
static void error_Closed(object sender, EventArgs e)
{
Application.Current.RootVisual.SetValue(Control.IsEnabledProperty, true);
}

You can subclass the ChildWindow and explicitly set the RootVisual to enabled. Source
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
namespace DST_Common_Silverlight_Controls
{
/// <summary>
/// Bug in ChildWindow sometimes leaves app disabled.
/// </summary>
public class ChildWindowEx : ChildWindow
{
protected override void OnClosed(EventArgs e)
{
base.OnClosed(e);
Application.Current.RootVisual.SetValue(Control.IsEnabledProperty, true);
}
}
}
Then just use the new type instead of ChildWindow in xaml like this:
<slcommon:ChildWindowEx
x:Class="DST.AvSyncMonitor.Silverlight.Gui.ErrorWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:slcommon="clr-namespace:DST_Common_Silverlight_Controls;assembly=DST.Common.Silverlight.Controls"
xmlns:controls="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls"
Title="Error">
<Grid x:Name="LayoutRoot" Width="540">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="Auto"/>
<RowDefinition/>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBlock x:Name="IntroductoryText" Grid.Row="0" Margin="0"
Text="An unknown error was encountered. Please contact your administrator for more information."/>
<StackPanel x:Name="ContentStackPanel" Grid.Row="2" Margin="0,6,0,0">
<TextBlock x:Name="LabelText" TextWrapping="Wrap" Margin="0,0,0,2"
Text="Error details"/>
<TextBox x:Name="ErrorTextBox" Height="90" TextWrapping="Wrap" IsReadOnly="True"
VerticalScrollBarVisibility="Auto"/>
</StackPanel>
<Button x:Name="OKButton" Grid.Row="3" Click="OKButton_Click"
Width="75" Height="23" HorizontalAlignment="Right" Margin="0,10,0,0"
TabIndex="0" Content="OK"/>
</Grid>
</slcommon:ChildWindowEx>

WPF Databinding Question

I've written a very short app in which I'm trying to achieve the following : have the CheckBox change its state from code. I've wired up the INotifyPropertyChanged interface and was expecting to see some results but apparently the app does nothing. Is there something wrong with the databinding?
Window1.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Threading;
namespace WpfTEST
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window, INotifyPropertyChanged
{
public Window1()
{
InitializeComponent();
this.Loaded += new RoutedEventHandler(Window1_Loaded);
this.PropertyChanged += new PropertyChangedEventHandler(Window1_PropertyChanged);
}
public bool Flag
{
get { return m_flag; }
set
{
m_flag = value;
OnPropertyChanged("Flag");
}
}
private bool m_flag = false;
void Window1_Loaded(object sender, RoutedEventArgs e)
{
this.m_cbox.DataContext = this;
for (int i = 0; i < 1000; i++)
{
Flag = (i % 2 == 0);
Thread.Sleep(200);
}
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged(string name)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
void Window1_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
}
#endregion
}
}
Window1.xaml
<Window x:Class="WpfTEST.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300" x:Name="window">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.5*" />
<ColumnDefinition Width="0.5*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="0.5*" />
<RowDefinition Height="0.5*" />
</Grid.RowDefinitions>
<CheckBox x:Name="m_cbox" Content="Let's see what happens" Grid.Row="2" Grid.Column="2" Grid.RowSpan="1" Grid.ColumnSpan="1" IsChecked="{Binding Path=Flag, ElementName=window, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</Grid>
</Window>

The only real problem I see with your code is the sleep loop in Loaded. That causes the UI thread to go unresponsive for the duration of the loop, since you're putting the UI thread into a blocked state.
There's a better way to test if you can change the flag from code and have your binding fire. Add a button to the window, hook up a click handler to the button, and in that click handler, toggle Flag -- I made those modifications to your original code (and removed the sleep loop), clicking on the button toggles the checkbox's state in the fashion you seem to desire.
<Window x:Class="WpfTEST.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300" x:Name="window">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.5*" />
<ColumnDefinition Width="0.5*" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="0.5*" />
<RowDefinition Height="0.5*" />
</Grid.RowDefinitions>
<!-- I added this button: -->
<Button Click="Button_Click" Grid.Row="0" Grid.Column="0"/>
<CheckBox x:Name="m_cbox" Content="Let's see what happens" Grid.Row="2" Grid.Column="2" Grid.RowSpan="1" Grid.ColumnSpan="1" IsChecked="{Binding Path=Flag, ElementName=window, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</Grid>
</Window>
and in code behind:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Threading;
namespace WpfTEST {
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window, INotifyPropertyChanged {
public Window1() {
InitializeComponent();
this.Loaded += new RoutedEventHandler(Window1_Loaded);
this.PropertyChanged += new PropertyChangedEventHandler(Window1_PropertyChanged);
}
public bool Flag {
get { return m_flag; }
set {
m_flag = value;
OnPropertyChanged("Flag");
}
}
private bool m_flag = false;
void Window1_Loaded( object sender, RoutedEventArgs e ) {
this.m_cbox.DataContext = this;
Flag = false;
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
public void OnPropertyChanged( string name ) {
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(name));
}
void Window1_PropertyChanged( object sender, PropertyChangedEventArgs e ) {
}
#endregion
private void Button_Click( object sender, RoutedEventArgs e ) {
Flag = !Flag;
}
}
}
Other than the above modifications to add the button and its click handler, and remove that sleep loop, I made no modifications to your original code (although you could streamline it a bit).

That will only work if your Flag property is a dependency property. To get this working in the simplest way i can think of i would do the following :
change your binding to be :
IsChecked="{Binding Path=Flag,Mode=TwoWay}"
and in your constructor in your code behind do this :
DataContext = this;
or in XAML
DataContext="{Binding RelativeSource={RelativeSource self}}"
Note : Flag does not need to be a dependency property if you are setting the datacontext to be the window.