This is a mostly out of curiosity question and to hopefully help me better understand binding, XAML, and extension syntax. 

So I simply want to change the binding source from the MainWindow to an object I have instantiated in MainWindow. 

Here is my C# code:

```
    public partial class MainWindow : Window, INotifyPropertyChanged
    {

        public MainWindow()
        {
            favclass myfavclass = new favclass();
            InitializeComponent();
            this.DataContext = this;
        }

        string _myString = "hello";
        public string MyString
        {
            get { return _myString; }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        void OnPropertyChanged(string propName)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(
                    this, new PropertyChangedEventArgs(propName));
        }

    }

    public class favclass : INotifyPropertyChanged
    {
        int _myint = 34;
        public int MyInt
        {
            get { return _myint; }
            set { _myint = value; }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        void OnPropertyChanged(string propName)
        {
            if (this.PropertyChanged != null)
                this.PropertyChanged(
                    this, new PropertyChangedEventArgs(propName));
        }

    }

}

```

and my XAML

```
<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525" >
    <Grid>
        <TextBlock Height="50" Width="50" Text="{Binding MyString}"/>
        <TextBlock Height="50" Width="48" Margin="200,100,100,100" 
                   Text="{Binding Source=myfavclass, Path=MyInt}"/>

    </Grid>
</Window>

```

So as you can see I want first display the MyString property from main window.

Then I want to display the MyInt from the myfavclass object. But of course MyInt doesn't appear. I've tried every variation I can think of.

What XAML am I missing? Why doesn't the XAML I have work?

Thanks