Related to @Duo Xu's response, Microsoft released a preview of their .NET ProtoBuf client for Phoenix (hdinsight-phoenix-sharp) on Nuget.org in June 2016. I've found it worked well against my HDP 2.4 (HBASE 1.1.2 / Phoenix 4.4) cluster, but the API was unfamiliar to me. As I learned it, I implemented an IDbConnection, IDbCommand et al wrapper API around it, named Garuda.Data. It makes access to Phoenix from .NET code feel almost like SqlConnection, SqlCommand, etc - Check it out on Nuget: https://www.nuget.org/packages/Garuda.Data/
Blog post on the topic: http://dwdii.github.io/2016/08/13/Garuda.Data-Apache-Phoenix-For-.NET-Developers.html
Garuda.Data Github Repo: https://github.com/dwdii/GarudaUtil