Set DataContext in XAML
Just change the Window to bind DataContext to itself:
<Window x:Class="WpfApplication2.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300" DataContext="{Binding RelativeSource={RelativeSource Self}}" ... />
I believe the DataContext in this scenario is implicit and does not have to be set since you are using the code behind. If you were using MVVM you would add a reference to that folder and class inside of you XAML markup and set the resource key equal to a value that can then be declared as the DataContext inside of a child elements DataContext property. But in your case (since you are not using MVVM) you shouldn't have to do that.