User defined top level control in XAML

A normal UserControl looks like this in XAML:

<UserControl x:Class="mynamespace.foo" ...namespaces...>
<!-- content -->
</UserControl>

I'd like to be able to define my own top level object, along the lines of:

<MyControl x:Class="mynamespace.mycontrol" ...namespaces...>
<!-- content -->
</UserControl>

Where MyControl derives from a UserControl itself.

Of course the compiler complains about "MyControl" not being found. Is there a way around this?

Solution

The root tag is the base class. That's why the root of the default Window1 is Window. Using the menu option Add > UserContol... is in fact creating a sub-class for UserContol.

If you have some common elements and want a control base class you can use the base class as the root tag. You can't derive your class from any class that has a xaml defined visual tree, but your base class can derive from UserConrtol.

First define your base class:

public class MyControlBase : UserControl
{
    // ...
}

Then create your specific child class:

(You can start with the automatically created UserControl1 and change it from there)

public partial class MyControl1 : MyControlBase
{
    public MyControl1()
    {
        InitializeComponent();
    }
}

Then change the Xaml side to look like this:

<MyNamespace:MyControlBase
    x:Class="MyNamespace.MyControl1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:MyNamespace="clr-namespace:MyNamespace">

This is a great way to make custom controls derived from built in ones other that UserControl. It is typically recommended to just use basic UserConrtols if you can and make a custom control only if you have to.

good luck,