Silverlight TabControl Inheritance Fails in Expression Blend.

Question

I create a basic TemplatedControl via Visual Studio. I then inherit TabControl instead of Control. It technically works (ie passes compile) but inside Expression Blend 3, I get an error " object reference not set to an instance of an object".

Then if i click on the TabItem itself, the error goes away? anyone experience this?

I tested this out on a brand new project with nothing it other than a custom tab control and same thing happens (so it could very well be an expression bug?)

Code is here:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace Riagenic.UXLib.Controls.Chrome
{
    public class ChromeTabControl : TabControl
    {
        public ChromeTabControl() : base()
        {
            this.DefaultStyleKey = typeof(ChromeTabControl);

        }
    }
}

Answer 1

It turns out it was a bug in Expression Blend 3. Work around (Via Peter Blois - Program Manager on Expression Blend and rockstar) says to put this in place:

This appears to be a bug in Blend 3- I can repro in Blend 3 but not in our more recent builds. It’s trying to find the SelectedIndexProperty static on your custom TabControl and failing.

A workaround is to add the code (not ideal since you’ll get parse warnings):

namespace Riagenic.UXLib.Controls.Chrome {
      public class ChromeTabControl : TabControl {
            public ChromeTabControl()
                  : base() {
                  this.DefaultStyleKey = typeof(ChromeTabControl);

            }

            public static readonly DependencyProperty SelectedIndexProperty = DependencyProperty.Register("SelectedIndex", typeof(int), typeof(ChromeTabControl), new PropertyMetadata(0));
      }
}