MyUserControl cannot be the root of a XAML file because it was defined using XAML
c#, wpf, xaml
Solution
You are not meant to do that and the error tells you that.
Besides, using XAML you set the `Content`, if you set it again in your derived control you would lose everything you defined before. If you want inheritance and reusability use a custom control (and create a respective `ControlTemplate`).
Problem
Possible Duplicate: Inheriting from a UserControl in WPF I'm trying to create a WPF user control, which is derived from an other user control, which I also have defined. ``` <myNamespace:NavigationControl 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:myNamespace="clr-namespace:myNamespace" mc:Ignorable="d" x:Class="myNamespace.WelcomeScreen" x:Name="UserControl" d:DesignWidth="640" d:DesignHeight="480"> ``` and here's what WelcomeScreen.cs looks like: ``` public partial class WelcomeScreen : NavigationControl { public WelcomeScreen() { this.InitializeComponent(); } } ``` When I compile this, I get following error: 'myNamespace.NavigationControl' cannot be the root of a XAML file because it was defined using XAML. What am I doing wrong?