If you are interested in building REST APIs on .NET in C#, you should look at the tutorials on <a href="http:&#x2F;&#x2F;www.asp.net&#x2F;web-api" rel="nofollow">http:&#x2F;&#x2F;www.asp.net&#x2F;web-api</a> or for MVC style web development try <a href="http:&#x2F;&#x2F;www.asp.net&#x2F;mvc" rel="nofollow">http:&#x2F;&#x2F;www.asp.net&#x2F;mvc</a>.<p>With a free Azure account you can be up and running in no time with a working API.<p>If you are interested in C# development for REST APIs that will run on Mono under Linux, then take a look at Nancy <a href="http:&#x2F;&#x2F;nancyfx.org&#x2F;" rel="nofollow">http:&#x2F;&#x2F;nancyfx.org&#x2F;</a> and ServiceStack <a href="https:&#x2F;&#x2F;servicestack.net&#x2F;" rel="nofollow">https:&#x2F;&#x2F;servicestack.net&#x2F;</a>.<p>P.S. ServiceStack v3 is open source and free. ServiceStack v4 is open source and requires a license.