I created this repository because existing solutions do not allow me to use the entered value if it doesn't exist in the suggestion list.
I was inspired by Eric Pap's Autocomplete Textbox project (https://www.codeproject.com/Articles/795010/An-easy-to-use-WPF-Autocomplete-Textbox) and this article written by Asma Khalid https://www.c-sharpcorner.com/article/wpf-auto-completesuggestion-text-box-control2/
I tried to modify Eric Pap's project to achieve my goal but I failed since it's too complex/a spaghetti code and uses Rx. Asma Khalid solution is fine but needs some small improvements.