Question

Having a simple XAML user control, I’d like to set the DataContext to the code behind (xaml.cs) file.

I’d like to set DataContext and Itemssource in XAML, so I can populate the combobox with property ListOfCars

XAML

<UserControl x:Class="Sample.Controls.MyControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" 
             d:DesignHeight="85" d:DesignWidth="200">
    <Grid Height="85" Width="200" Background="{StaticResource MainContentBackgroundBrush}">
        <StackPanel Orientation="Vertical">                
            <ComboBox Height="23.338" x:Name="CarList" />                
        </StackPanel>    
    </Grid>
</UserControl>

Code behind

public List<Cars> ListOfCars
{
  get { return _store.ListCars(); }
}

In other words, instead of doing this in codebehind, how may I set the binding in XAML

public MyControl()
{
  InitializeComponent();
  _store = new Store();
  CarList.ItemsSource = _store.ListCars();
  CarList.DisplayMemberPath = "Name";
}

Answer 1

Just bind the ItemsSource.

<ComboBox ItemsSource="{Binding ListOfCars}"/>

And then for the UserControl:

<MyControl DataContext="{Binding *viewModel*}"/>

You have to bind the DataContext where your UserControl is used rather than in the definition, because in the definition you don’t know to what to bind. The Combobox automatically is in the context of the control so you can just bind to the DataContext without any additional work.

Example of binding to a resource:

<Application.Resources>
  ...
  <viewmodels:ViewModelLocator x:Key="ViewModelLocator"/>
  ...
</Application.Resources>


<MyControl DataContext="{Binding Source={StaticResource ViewModelLocator}}"/>

This creates an instance of the ViewModelLocator and then binds the DataContext of the control to that resource.