Getting weird behaviours when changing the binding to the TreeView - wpf

Question

I have ObservableCollection Fathers which contains property ObservableCollection Sons.
And I'm displaying it on the TreeView setting its DataContext property.
The Sons property displays as a ListBox of radio button under each Father - binded to ItemsSource.
First time setting the DataContext of the tree view to the fathers list, everything is working good. The radio buttons are checked according to the data.
Now, I'm setting the TreeView.DataContext to null - so the data will disappear. and then back to the original Fathers ObservableCollection which I set in the first time.
And now from some reason the radio buttons stopped being synchronized with the son object.
And I got deeper and I saw that the setter in the son object (that binded to the radio button) is raised with false from some reason. I Guess something related to the binding.
Is there any cache that the TreeView, or the ObservableCollection is saving after binding ? I want it to work like the first time I set the bind - Which there like it should only the getter is being called like it should.
Thanks.
This is my Tree view
<UserControl x:Class="Tester.CTLMyTree"
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:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">
<Grid x:Name="LayoutRoot" Background="White">
<Border Background="#FF919191" BorderThickness="1" CornerRadius="5"
HorizontalAlignment="Left" VerticalAlignment="Top"
Padding="5" BorderBrush="Black" Height="207" Width="190">
<Border.Resources>
<sdk:HierarchicalDataTemplate x:Key="LayerListTemplate">
<StackPanel Orientation="Vertical" Width="200" >
<TextBlock Text="Hello"/>
<ListBox x:Name="lstViews" ItemsSource="{Binding Sons}" BorderThickness="0" Width="200">
<ListBox.ItemTemplate>
<DataTemplate>
<RadioButton Content="Check" IsChecked="{Binding IsChecked, Mode=TwoWay}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
</sdk:HierarchicalDataTemplate>
</Border.Resources>
<sdk:TreeView ItemsSource="{Binding}" ItemTemplate="{StaticResource LayerListTemplate}" x:Name="myTreeView" />
</Border>
</Grid>
</UserControl>
The Objects behind
public class CCFather
{
public CCFather()
{
Sons = new ObservableCollection<CCSon>();
}
public ObservableCollection<CCSon> Sons
{
get;
set;
}
}
public class CCSon
{
private bool m_blnChecked;
public bool IsChecked
{
get
{
return m_blnChecked;
}
set
{
m_blnChecked = value;
}
}
}
In my application i added this treeview control and called it m_objSimpleTree.
This code is the initializing
m_objItems = new ObservableCollection<CCFather>();
CCFather objItem1 = new CCFather();
objItem1.Sons.Add(new CCSon());
objItem1.Sons[0].IsChecked = true;
m_objItems.Add(objItem1);
m_objSimpleTree.myTreeView.DataContext = m_objItems;
And when i press a button i'm doing this
m_objSimpleTree.myTreeView.DataContext = null;
m_objSimpleTree.myTreeView.DataContext = m_objItems;
This code will raise already the IsChecked setter of the son to false (Why ???)
But the RadioButton will still be checked.
Second time pressing the button. it will be unchecked and the setter didn't raise.
When i'm pressing on the radio button It's raising twice the setter. First time with false
second with true.
Can't figure why it's happening.. The only think i can think of is that the treeview is saving something in the first binding or something like this.

Answer 1

It does so because you have used twoWay binding for the control
binding code project
In a two way binding when you change some thig on the view then the data gets saved in the object also . to which the datacontext is assigned. try oneWay for that . But need to be careful as if you wanna save data using twoWay one way might not help. MVVM suggests to use two way binding to save data but you want a refreshed list then create a new object :)
Also try clear Binding
Clear binding
Am not sure of the last link as never tried. Please o through it might get an idea. But since you might need a new object again so you can create a fresh object to assign to datacontext.
--- EDIT-----
Here's a xaml code
<UserControl
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:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk" x:Class="SilverlightSOApp.MainPage"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">
<Grid x:Name="LayoutRoot" Background="White">
<Border Background="#FF919191" BorderThickness="1" CornerRadius="5"
HorizontalAlignment="Left" VerticalAlignment="Top"
Padding="5" BorderBrush="Black" Height="207" Width="190">
<Border.Resources>
<sdk:HierarchicalDataTemplate x:Key="LayerListTemplate">
<StackPanel Orientation="Vertical" Width="200" >
<TextBlock Text="Hello"/>
<ListBox x:Name="lstViews" ItemsSource="{Binding Sons}" BorderThickness="0" Width="200">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<RadioButton Content="Check" GroupName="abcd" IsChecked="{Binding IsChecked, Mode=TwoWay}"/>
<RadioButton Content="Check" GroupName="abcd" IsChecked="{Binding IsChecked2, Mode=TwoWay}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</StackPanel>
</sdk:HierarchicalDataTemplate>
</Border.Resources>
<sdk:TreeView ItemsSource="{Binding}" ItemTemplate="{StaticResource LayerListTemplate}" x:Name="myTreeView" />
</Border>
<Button Content="Button" HorizontalAlignment="Left" Margin="303,268,0,0" VerticalAlignment="Top" Width="75" Click="Button_Click"/>
</Grid>
And the c#
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Browser;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
namespace SilverlightSOApp
{
public partial class MainPage : UserControl
{
private ObservableCollection<CCFather> m_objItems;
public MainPage()
{
InitializeComponent();
Loaded += new RoutedEventHandler(MainPage_Loaded);
}
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
m_objItems = new ObservableCollection<CCFather>();
CCFather objItem1 = new CCFather();
objItem1.Sons.Add(new CCSon());
objItem1.Sons[0].IsChecked = false;
m_objItems.Add(objItem1);
myTreeView.DataContext = m_objItems;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
myTreeView.DataContext = null;
myTreeView.DataContext = m_objItems;
}
}
public class CCFather
{
public CCFather()
{
Sons = new ObservableCollection<CCSon>();
}
public ObservableCollection<CCSon> Sons
{
get;
set;
}
}
public class CCSon
{
private bool m_blnChecked;
private bool m_blnChecked2;
public bool IsChecked
{
get
{
return m_blnChecked;
}
set
{
m_blnChecked = value;
}
}
public bool IsChecked2
{
get
{
return m_blnChecked2;
}
set
{
m_blnChecked2 = value;
}
}
}
}
Now the main point if you want to implement it for single radio button then you need to implement the Click event and set radio button to false and next time to true :) or else you need to use a checkbox one radio button once checked cannot be converted to false