User control

Idea is to create collection of buttons in user control.

So, first start new project (i.e. ItemsControl), and, for example, in same solution add new WPF User Control Library:

After enter XAML like: 

<UserControl x:Class="MyItemsControl.MyItemsControl"
             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 MyTest}">
            
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Button Content="Test"/>
                </DataTemplate>
            </ItemsControl.ItemTemplate>

        </ItemsControl>
    </Grid>
</UserControl>

Notice line:

<ItemsControl ItemsSource="{Binding MyTest}">

MyTest property will be hidden in another class (SomeAnotherClass), not in the main datacontext, which I will explain later. 

Now, save, and build the solution. In main project (ItemsControl), in references add your user control (MyItemsControl):

Write XAML like:

<Window x:Class="ItemsControl.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:myItemsControl="clr-namespace:MyItemsControl;assembly=MyItemsControl"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <myItemsControl:MyItemsControl DataContext="{Binding MyDataContext}"/>
    </Grid>
</Window>

Notice line:

<myItemsControl:MyItemsControl DataContext="{Binding MyDataContext}"/>

In code behind of main project (ItemsControl) I wrote something like:

public MainWindow()
{
  ItemsControlViewModel icvm;
  icvm = new ItemsControlViewModel();

  this.DataContext = icvm;
  InitializeComponent();
}

Then class ItemsControlViewModel looks like: 

public class ItemsControlViewModel
{
	public SomeAnotherClass MyDataContext { get; set; }

	public ItemsControlViewModel()
	{
		MyDataContext = new SomeAnotherClass();
	}
}

Notice that here I created MyDataContext as a property, and I referenced that class to another class (SomeAnotherClass) which looks like:

public class SomeAnotherClass
{
	public IEnumerable<string> MyTest { get; set; }

	public SomeAnotherClass()
	{
		MyTest = new[] { "test" };
	}
}

Here notice:

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

Which is property called from my user control, also notice that is of the type IEnumerable, that is because it is binded to ItemsControl.

Here you can download example.