How to bind multiple ComboBoxes to one Collection? [duplicate] - wpf

Question

This question already has an answer here:
WPF ComboBox bind itemssource to different datacontext in MVVM
(1 answer)
Closed 4 years ago.
I Need a collection of ComboBoxes with a common collection of possible selections.
Codebehind excerpt:
namespace ComboBoxesInCollection
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
D = new DataContainer();
this.DataContext = D;
}
private DataContainer D;
}
public class DataContainer
{
public ObservableCollection<Item> ComboboxItems
{
get { return comboboxItems; }
}
public ObservableCollection<Selection> ComboboxSelections
{
get { return comboboxSelections; }
}
public DataContainer()
{
comboboxItems = new ObservableCollection<Item>
{
new Item(100, "Entry #1"),
new Item(101, "Entry #2"),
new Item(102, "Entry #3")
};
comboboxSelections = new ObservableCollection<Selection>()
{
new Selection(1),
new Selection(2),
new Selection(3)
};
}
private ObservableCollection<Item> comboboxItems;
private ObservableCollection<Selection> comboboxSelections;
}
}
XAML excerpt:
<Window.Resources>
<DataTemplate x:Key="CSTemplate">
<Border BorderBrush="Black" BorderThickness="1,1,0,0" Margin="0,0,0,4" Padding="4">
<StackPanel>
<Label Content="{Binding Id}"/>
<ComboBox
ItemsSource="{Binding ComboboxItems}" //<= does not work
DisplayMemberPath="Name"
SelectedValue="{Binding SelectedId}"
SelectedValuePath="Id"
/>
</StackPanel>
</Border>
</DataTemplate>
...
<ItemsControl ItemsSource="{Binding ComboboxSelections}" ItemTemplate="{StaticResource CSTemplate}"/>
The ItemsControl shows the items, but the Combobox is empty.
I know that i try to access a property/collection inside of a Selection that is not existing right now.
How would i correctly specify the DataBinding so i can see the items?

Answer 1

Used Element Binding to access the DataContext Property of the window.
First Name the Window x:Name="Window1" and the while binding, use element binding.
ItemsSource="{Binding ElementName=Window1, Path=DataContext.ComboboxItems}"
XAML of whole window
<Window x:Class="WpfApp6.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:WpfApp6"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800" x:Name="Window1">
<Window.Resources>
<DataTemplate x:Key="CSTemplate">
<Border BorderBrush="Black" BorderThickness="1,1,0,0" Margin="0,0,0,4" Padding="4">
<StackPanel>
<Label Content="{Binding Id}"/>
<ComboBox
ItemsSource="{Binding ElementName=Window1, Path=DataContext.ComboboxItems}"
DisplayMemberPath="Name"
SelectedValue="{Binding SelectedId}"
SelectedValuePath="Id"
/>
</StackPanel>
</Border>
</DataTemplate>
</Window.Resources>
<Grid>
<ItemsControl ItemsSource="{Binding ComboboxSelections}" ItemTemplate="{StaticResource CSTemplate}" />
</Grid>