C# Rank Checker like Moz

I'm just wondering if anyone has made a rank checker similar to on moz pro.

If so, what API did you use, programming language (although, I'd prefer to use c# for this task) and did you find any free/low cost API that can look up about 50 kw per day?

There are APIs out there that will fetch you search results but it's quite easy to just scrape the data yourself from the SEs. For C# you can use HtmlAgilityPack to parse the results. By the time you find the right API to get set up with - you probably could have just scraped it yourself.