show state lbox when txbox entered not show when leaving

Clarification:
On my Windows Form entry form I would use a text box for entry of the value for state - i.e. Texas, California, etc. Rather than have the user type the entry, I would provide a list box populated with all of the state names and allow them to either use their mouse to make a selection or to start typing and filter and update the list box to show only those items that contained the characters as they were entered. So the use would type t and the list box would show only Texas, and Tennessee. When their entry reached a point where there was only one selection remaining the value would be placed in the text box and the next entry item would receive focus.

To activate the state list box I would trap the enter event for the state text box to set the list box visible = true and trap the leave event for setting the list box to visible = false. 

I am trying to duplicate this in WPF without success and am requesting assistance in how to best approach duplicating the above Windows Forms behavior in WPF.

i didn't get your point. Please provide clear details.