WPF: how to recreate ItemContainer? - wpf

Question

Following my previous question How to change ComboBox item visibility, since the problem is slightly changed i decided to open a new post to solve the it. For those who don't want to read all the comments on the previous post, here is the situation.
I have a DataGrid that is generated at run time. Each column of this datagrid have a combobox inside the header. All those comboboxes have the same Source, that is an observable collection of a class item. Every item show a property that i use in the ItemContainerStyle of the comboboxes, to decide whether each ComBoBoxItem should be Visible or not.
Now, as far as i know, WPF work this way : if a view contain controls like combobox or treeview, then their items (i.e. ComboBoxItem, TreeViewItem...), won't be generated until it's not necessary (for example when the dropdown of a combobox is opened). If i apply an ItemContainerStyle, this will tell to the target how its items should be created. The problem is, that at the moment that this items are generated, every change i need to apply to the style, won't be saved.
Here is my code:
<DataGrid HeadersVisibility="Column" Name="griglia" Grid.Row="2" ItemsSource="{Binding Path=Test}" AutoGenerateColumns="True" IsReadOnly="True" ScrollViewer.CanContentScroll="True" ScrollViewer.VerticalScrollBarVisibility="Visible" ScrollViewer.HorizontalScrollBarVisibility="Visible">
<DataGrid.ColumnHeaderStyle>
<Style TargetType="{x:Type DataGridColumnHeader}">
<Setter Property="ContentTemplate" >
<Setter.Value>
<DataTemplate DataType="DataGridColumnHeader" >
<ComboBox ItemContainerStyle="{StaticResource SingleSelectionComboBoxItem}" DisplayMemberPath="Oggetto" Width="100" Height="20" ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type DataGrid}},Path=DataContext.Selezione, UpdateSourceTrigger=LostFocus}" SelectionChanged="SingleSelectionComboBox_SelectionChanged">
</ComboBox>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
</DataGrid.ColumnHeaderStyle>
</DataGrid>
ItemContainerStyle:
<Style x:Key="SingleSelectionComboBoxItem" TargetType="ComboBoxItem" BasedOn="{StaticResource {x:Type ComboBoxItem}}">
<Style.Triggers>
<DataTrigger Binding="{Binding Selezionato}" Value="True">
<!-- Hide it -->
<Setter Property="Visibility" Value="Collapsed" />
<!-- Also prevent user from selecting it via arrows or mousewheel -->
<Setter Property="IsEnabled" Value="False" />
</DataTrigger>
</Style.Triggers>
</Style>
SelectionChanged:
private void SingleSelectionComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
foreach (var item in e.RemovedItems.OfType<PopolazioneCombo>())
{
item.Selezionato = false;
}
foreach (var item in e.AddedItems.OfType<PopolazioneCombo>())
{
item.Selezionato = true;
}
}
My requirement is that, if in any of the N combobox an item is selected, then, that item cannot be selected by anyone, until he lose the SelectedItem status. For instance let's assume i have 2 combobox and a collection of 4 Item (x,y,a,b) . If x is selected in ComboBox1, then x can't be selected in none of the 2 ComboBox until the SelectedItem of the ComboBox1 change (from x to y for instance). Now i can even accept the fact that the item in the dropdown is just disabled if it makes the things easier, i just need the fact that it cannot be selected again if he is already selected.
The problem is that this solution work for every ComboBox that has its ItemContainerGenerator.Status = NotStarted (this means that the ComboBoxItem are still not created). If i open the dropdown of a combobox, then its ComboBox items will retain their style no matter what i do (cause ItemContainerGenerator.Status = ContainersGenerated), while the combobox that i didn't opened keep track of the changes in the visibility of the items.
I'm Looking for a solution to recreate these items do that the new style with the changes in the visibility will be applied

Answer 1

after a lucky research on internet (i.e. i've found the correct combination of keyword), i found this wonderful method, so here the updated solution:
private void ComboBox_DropDownOpened(object sender, EventArgs e)
{
ComboBox c = sender as ComboBox;
c.Items.Refresh();
}
add this event in the xaml so that it became:
<ComboBox DropDownOpened="ComboBox_DropDownOpened" ItemContainerStyle="{StaticResource SingleSelectionComboBoxItem}" DisplayMemberPath="Oggetto" Width="100" Height="20" ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type DataGrid}},Path=DataContext.Selezione, UpdateSourceTrigger=LostFocus}" SelectionChanged="SingleSelectionComboBox_SelectionChanged"/>
and magically the combobox show the correct changes. Now i'm not a big fan of code behind, so if there is a way to do this adding a property to my Collection, or via xaml it would be better