Are CLR wrappers for dependency properties optional or not?

I was under the impression that CLR wrappers for dependency properties were optional under WPF, and just useful for setting within your own code.

However, I have created a UserControl without wrappers, but some XAML that uses it will not compile without them:

namespace MyControlLib
{
    public partial class MyControl : UserControl
    {
        public static readonly DependencyProperty SomethingProperty;

        static MyControl()
        {
            SomethingProperty = DependencyProperty.Register("Something", typeof(int), typeof(MyControl));
        }
    }
}

XAML usage:

<Window  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:ctrl="clr-namespace:MyControlLib;assembly=MyControlLib">

   <ctrl:MyControl Something="45" />

</Window>

Trying to compile this gives:

error MC3072: The property 'Something' does not exist in XML namespace 'clr-namespace:MyControlLib'. Line 开发者_开发百科blah Position blah.

Adding a CLR wrapper in MyControl.xaml.cs like:

public int Something
{
    get { return (int)GetValue(SomethingProperty); }
    set { SetValue(SomethingProperty, value); }
}

means it all compiles and works fine.

What am I missing?

You could use dependency properties without wrappers inside runtime bindings, but to set the property like you want you must have C# property to allow xaml compiler to compile your code.

I believe it will compile without the wrappers if you specify the namespace prefix on the property.

They are optional, but without them the property does not show up in the XAML designer automatically

<ctrl:MyControl ctrl:MyControl.Something="45" />