Idea was to write small app which will have one combo box where user will be able to change template for some list of buttons.

Instead I just made one project where I merged knowledge from this, this, this, and this article.

That is just for my future reference. Example project you can download from here.

Now idea is to have one control inside ItemsControl, and everything that inside UserControl, something like:

<UserControl x:Class="MyUserControl.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="300" d:DesignWidth="300">
    <Grid>
      
      <ItemsControl ItemsSource="{Binding myLabels}">
        <ItemsControl.ItemTemplate>
          <DataTemplate>
            <Label Content="{Binding DataContext.myContent, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}"/>
          </DataTemplate>
        </ItemsControl.ItemTemplate>
      </ItemsControl>
      
    </Grid>
</UserControl>

Here notice line:

<Label Content="{Binding DataContext.myContent, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}"/>

This line was taken from here.

My MainWindow.xaml looks like this:

<Window x:Class="UserControlDataContext.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:myUserControl="clr-namespace:MyUserControl;assembly=MyUserControl"
        xmlns:viewModel="clr-namespace:UserControlDataContext.ViewModel"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
      
        <Grid.Resources>
          <viewModel:UserControlDataContextViewModel x:Key="UserControlDataContextViewModel" />
        </Grid.Resources>
      
        <myUserControl:myControl DataContext="{Binding Source={StaticResource UserControlDataContextViewModel}}"/>
      
    </Grid>
</Window>

and view model like:

public class UserControlDataContextViewModel
{
	public string myContent { get; set; }

	public IEnumerable<string> myLabels { get; set; }

	public UserControlDataContextViewModel()
	{
		myContent = "test";
		myLabels = new[] { "test1", "test2" };
	}
}

Example project you can download from here.

In this article I want to extend my ItemsControl.Style, by binding template.

XAML:

<Grid>

	<Grid.Resources>
		<itemsControlItemTemplate:ItemsControlViewModel x:Key="ItemsControlViewModel" />
	</Grid.Resources>

	<ItemsControl DataContext="{StaticResource ItemsControlViewModel}" ItemsSource="{Binding myItemsSource}">

		<ItemsControl.Style>
			<Style TargetType="ItemsControl">
				<Style.Triggers>

					<DataTrigger Binding="{Binding ParentMyItemType}" Value="{x:Static itemsControlItemTemplate:myItemTypes.WrapPanel}">
						<Setter Property="ItemsPanel">
							<Setter.Value>
								<ItemsPanelTemplate>
									<WrapPanel />
								</ItemsPanelTemplate>
							</Setter.Value>
						</Setter>
					</DataTrigger>

					<DataTrigger Binding="{Binding ParentMyItemType}" Value="{x:Static itemsControlItemTemplate:myItemTypes.StackPanel}">
						<Setter Property="ItemsPanel">
							<Setter.Value>
								<ItemsPanelTemplate>
									<StackPanel />
								</ItemsPanelTemplate>
							</Setter.Value>
						</Setter>
					</DataTrigger>

				</Style.Triggers>
			</Style>
		</ItemsControl.Style>

		<ItemsControl.ItemTemplate>
			<DataTemplate>
			
				<DataTemplate.Resources>
					<itemsControlItemTemplate:AnotherModel x:Key="AnotherModel" />
				</DataTemplate.Resources>

				<Label DataContext="{StaticResource AnotherModel}" Content="{Binding myContent}" />

			</DataTemplate>
		</ItemsControl.ItemTemplate>

	</ItemsControl>

</Grid>

Here notice part, for example:

<DataTrigger Binding="{Binding ParentMyItemType}" Value="{x:Static itemsControlItemTemplate:myItemTypes.WrapPanel}">
	<Setter Property="ItemsPanel">
		<Setter.Value>
			<ItemsPanelTemplate>
				<WrapPanel />
			</ItemsPanelTemplate>
		</Setter.Value>
	</Setter>
</DataTrigger>

Where myItemTypes.WrapPanel I declared something like:

public enum myItemTypes
{
	WrapPanel,
	StackPanel
}

and then my view model looks like:

public class ItemsControlViewModel
{
	public IEnumerable<string> myItemsSource { get; set; }

	public myItemTypes ParentMyItemType { get; set; }

	public ItemsControlViewModel()
	{
		myItemsSource = new[] { "Test1", "Test2" };
		this.ParentMyItemType = myItemTypes.WrapPanel;
	}
}

public class AnotherModel
{
	public string myContent { get; set; }

	public AnotherModel()
	{
		myContent = "test2";
	}
}

notice line:

this.ParentMyItemType = myItemTypes.WrapPanel;

with that line I said that I want my style to be with StackPanel.

Example code you can download from here.

I am still learning DataTemplate, but at this moment I would like just to underline (as a note to myself) that it seems that binding for DataTemplate goes to another class.

XAML:

<Window x:Class="ItemsControlItemTemplate.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:itemsControlItemTemplate="clr-namespace:ItemsControlItemTemplate"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Grid>

      <Grid.Resources>
        <itemsControlItemTemplate:ItemsControlViewModel x:Key="ItemsControlViewModel" />
      </Grid.Resources>
      
      <ItemsControl DataContext="{StaticResource ItemsControlViewModel}" ItemsSource="{Binding myItemsSource}">
        <ItemsControl.ItemTemplate>
          <DataTemplate>
            
              <DataTemplate.Resources>
                <itemsControlItemTemplate:AnotherModel x:Key="AnotherModel" />
              </DataTemplate.Resources>
            
              <Label DataContext="{StaticResource AnotherModel}" Content="{Binding myContent}" />
            
          </DataTemplate>
        </ItemsControl.ItemTemplate>
      </ItemsControl>
      
    </Grid>
</Window>

Here note part:

<DataTemplate.Resources>
	<itemsControlItemTemplate:AnotherModel x:Key="AnotherModel" />
</DataTemplate.Resources>

<Label DataContext="{StaticResource AnotherModel}" Content="{Binding myContent}" />

My view model:

public class ItemsControlViewModel
{
	public IEnumerable<string> myItemsSource { get; set; }

	public ItemsControlViewModel()
	{
		myItemsSource = new[] { "Test1", "Test2" };
	}
}

public class AnotherModel
{
	public string myContent { get; set; }

	public AnotherModel()
	{
		myContent = "test";
	}
}

Here notice class:

public class AnotherModel
{
	public string myContent { get; set; }

	public AnotherModel()
	{
		myContent = "test";
	}
}

Which is actually in use in the label under the datatemplate

Example project you can download from here.