Need recommendation for some search libaries and related controls (winforms)

I have a few search fields to make. I want the user to type in a few characters and have a box appear below showing some possible answers.

The winforms autocomplete only shows answers where the first few characters of the answer exactly match the first few characters they type. As far as I've read there's no way to change this behavior.

I was just wondering if you guys knew of some prebuilt search libraries for C# and winforms that contain both an engine for intelligent result suggestion (sort of like google's) and controls that have dro开发者_运维技巧p down boxes to contain these suggestions.

I'd prefer open source, but if the library is really good I'd certainly pay a few hundred bucks for it.

Any thoughts?

Isaac