Bind DataContext to Current Window in WPF

XAML way

DataContext="{Binding RelativeSource={RelativeSource Self}}"

DataContext="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorLevel=1,AncestorType=UserControl}}">

<UserControl ... DataContext="{Binding RelativeSource={RelativeSource Self}}">
</UserControl>

C# way

using System;
using System.Windows;

namespace WpfTutorialSamples.DataBinding
{
    public partial class DataContextSample : Window
    {
        public DataContextSample()
        {
            InitializeComponent();
            this.DataContext = this;
        }
    }
}

References
https://stackoverflow.com/questions/12430615/datacontext-and-binding-self-as-relativesource
https://wpf-tutorial.com/data-binding/using-the-datacontext/
https://stackoverflow.com/questions/11995318/how-do-i-bind-to-relativesource-self
https://stackoverflow.com/questions/20420001/how-to-set-datacontext-to-self