Combobox with .txt

Question

Good morning c# experts,
I have another question for you:  Is it possible to populate a combobox with data in a txt file?
For example:  I have a textbox (textbox1) where the user enters a building number and based on that input, combobox1 would populate with all the room numbers associated with that building.  I already have a txt file with all the corresponding information:
 
439:  123, 124, 424, 136
321:  134, 843, 339, 399]
 
So, if the user enters 439 into textbox1, combobox1 would populate with 123, 124, 424, 136.  IS that possible?