Hello, 

Thank you for posting. 

I have made a sample project where I search the visual tree for the SpecializedtextBox element. That element displays the SelectedItem’s text in the XamComboEditor. Then I call the SelectAll method and the text is selected when the XamComboEditor gets the focus. Please see the attached project and feel free to let me know if it helps you. 

As this is not a supported feature for the control, I have logged it as a new product idea.  I have sent your product idea directly to our product management team.  Our product team chooses new product ideas for development based on popular feedback from our customer base.  Infragistics continues to monitor application development for all of our products, so as trends appear in requested features, we can plan accordingly.

We value your input, and our philosophy is to enhance our toolset based on customer feedback.  If your feature is chosen for development, you will be notified at that time.  Your reference number for this product idea is PI12110112.