Question

As UIElement has no property DataContext, how can I get the DataContext for UIElement?

Answer 1

The DataContext property is introduced to the inheritance hierarchy in the FrameworkElement.

Because FrameworkElement inherits from UIElement you have to make sure the UIElement actually is a FrameworkElement:

if(uiElement is FrameworkElement frameworkElement)
{
    var dc = frameworkElement.DataContext;
}