Why running a selected single coded step fails?

Problem

When a single coded step is selected and run it fails with the following exception:

System.ArgumentNullException: Start reference element can't be null. Please make sure the DOM is loaded by either calling NavigateTo() to a page or add browser RefreshDomTree() prior to the code which needs the DOM.

Cause

This happens because a single coded step is not set to automatically call refresh of the DOM but at the same time it needs any DOM tree to execute against.

Solution

Add a statement to refresh the DOM tree as first row in the coded step.

// Use Manager.ActiveBrowser for a web application 
Manager.ActiveBrowser.RefreshDomTree();

// Use Manager.ActiveApplication for a wpf application 
Manager.ActiveApplication.MainWindow.RefreshVisualTrees();