You should have a look at the "AutoComplete" properties of the text box.
that let's you set the source for autocompletion (File System, last URL, browser history, custom, ...)
that let's you select the way suggestions are proposed to the user
that let's you set the list of suggestion (it is a string collection) when the AutoCompleteSource
is set to CustomSource
I hope those properties will help you solve your problem.