NxtLib is a .NET library that wraps around Json API in the Nxt platform (http://nxt.org/).
NxtLib simplifies the development process when integrating to Nxt as it translates all json data into typed .NET code.
Target framework versions: .NETFramework4.0, .NETFramework4.5 and .NET Platform Standard 1.3
It currently supports NXT version 1.11.3
There are a couple of example programs that you can check out.
The first example is checking the account balance and also sending some Nxt, you can check out the code here, or the youtube video where the code is explained in detail.
A bit more advanced is the local signing feature, where you sign the transaction within your .NET application. It's useful if you don't have any NXT node that can be trusted.
There's a sample code of how to use that here, and a youtube video explaining the functionality.
There's a thread about NxtLib on the nxtforum.org. You're welcome to join!