Visual Studio overwriting UserControl parent when not inheriting System.Windows.Controls.UserControl

Question

I am creating a series of UserControls that all have some similar business logic. So I tried to implement this common business logic in an abstract base class that all of these user controls would inherit from. The inheritance chain looks something like this:

System.Windows.Controls.UserControl <-- MyControlBase (abstract)<--MyControl1, MyControl2, etc.

I've created the MyControl1, MyControl2 etc. classes as User Controls in Visual Studio. I've set the classes to inherit from MyControlBase instead of System.Windows.Controls.UserControl. It works great... until I make a change in the XAML and re-save. Visual Studio 2008 then re-assigns the generated class to inherit from System.Windows.Controls.UserControl.

The code example of the classes and XAML are as follows:

// MyControlBase.cs:

    public abstract class MyControlBase.Windows.Controls.UserControl
    {
       public abstract void DoOperation1();
    }

// MyControlBase.xaml: none

// MyControl1.cs:

    public partial class MyControl1: MyControlBase
    {
        public MyControl1()
        {
            InitializeComponent();
        }
        public override void DoOperation1()
        {
           return;
        }
    }

// MyControl1.xaml:

    <UserControl x:Class="Test.Controls.BarChart"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
        <Grid x:Name="LayoutRoot" Background="Blue">

        </Grid>
    </UserControl>

// mycontrol1.g.cs (generated by Visual Studio) orginally

    public partial class MyControl1: System.Windows.Controls.UserControl
    {

        internal System.Windows.Controls.Grid LayoutRoot;

        // InitilizeComponent() etc

    }

// mycontrol1.g.cs (generated by Visual Studio) modified by me

public partial class MyControl1: MyControlBase
    {

        internal System.Windows.Controls.Grid LayoutRoot;

        // InitilizeComponent() etc
    }

Whenever editing MyControl1.xaml in the Visual Studio 2008 editor after saving it the modified mycontrol1.g.cs keeps reverting itself to the original one (namingly: inheriting again from System.Windows.Controls.UserControl). The compile then fails because the two partial classes of MyControl1 are not inheriting from the same parent: the VS generated one inherits from System.Windows.Controls.UserControl, my code behind from MyControlBase.

Is there a way to work around this issue? I would like to have the ability to inherit from an abstract class and assume there is a way for Visual Studio to let me, I just don't see what I'm missing. Or is the concept of a UserControl inheriting from another class than System.Windows.Controls.UserControl a bad concept?

Answer 1

You need to change your xaml to inherit from MyControlBase instead of UserControl:

<my:MyControlBase
  xmlns:my="MyNamespace"
  x:Class="Visiblox.Charts.Test.Controls.BarChart"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
   <Grid x:Name="LayoutRoot" Background="Blue">
   </Grid>
</my:MyControlBase>

That is why Visual Studio keeps changing the base class when you edit the xaml.

Answer 2

The answer from Bryant works (Thanks!) but the XAML design view in VS2008 will not display it. You'll get an error:

Error 20  Could not create an instance of type 'MyControlBase'.