How to access a code behind property of ResourceDictionary in another XAML file?

Question

Situation: There is ResourceDictionary Class1.xaml backed by code behind Class Class1.cs using x:Class. There is Property MyHeight inside Class Class1.cs .

Goal: To access Property MyHeight in XAML.

Problem: It doesn't compile giving the next error:

Exception thrown: 'System.Windows.Markup.XamlParseException' in PresentationFramework.dll Additional information: 'Provide value on 'System.Windows.StaticResourceExtension' threw an exception.' Line number '13' and line position '41'.

Workaround: It works in C# code.

Note: It works for separate Class or UserControl, but I need it for ResourceDictionary.

Question: How to access Property MyHeight of Class Class1.cs in MainWindow.xaml ?

Class1.xaml:

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:local="clr-namespace:WpfApplication2"
                x:Class="WpfApplication2.Class1">

Class1.cs:

    partial class Class1
{
    public Class1()
    {
        InitializeComponent();
    }

    public double MyHeight
    {
        get { return 20; }
        set { }
    }
}

MainWindow.xaml:

    <Window.Resources>
    <local:Class1 x:Key="MyClass"></local:Class1>
</Window.Resources>
<Grid>
    <Ellipse Fill="Red" Width="100" Height="{Binding Source={StaticResource MyClass}, Path=MyHeight}"></Ellipse>
</Grid>

MainWindow.xaml.cs:

    public partial class MainWindow : Window
{
    public MainWindow()
    {
        this.Resources.Add("key", new Class1());
        MessageBox.Show(((Class1)this.Resources["key"]).MyHeight.ToString()); // Works

        InitializeComponent();
    }
}

Answer 1

<Window.Resources>
    <ResourceDictionary>
        <local:Class1 x:Key="MyClass" />
    </ResourceDictionary>
</Window.Resources>

What's missing is the ResourceDictionary tag.

This also works (as a replacement for the above):

public Class1()
{
    InitializeComponent();
    Add("MyHeight", 20d);
}

InitializeComponent resets the Resources dictionary, which explains your "this works in code" -- if you try to retrieve "key" after, you won't get it.