Top 20 NuGet contract Packages

Design by contract programming support
Base classes (like suits, ranks, cards, auction, play, contract) that are helpful in creating a bridge card game.
Puresharp is a Framework that provides the essential APIs to productively build high quality (.NET 4.5.2+ & .NET Core 2.1+) applications through reliability, scalability and performance without no compromise.
IPuresharp urbanize libraries with strategic private code to lay transparent foundations for Puresharp API .NET
Neo.SmartContract.Framework
Contracts ensuring, Messanging, LINQ expression parser and extension methods, Task Parallel Library helpers, Type auto-mapping for storage and benchmark.
A simple tool for unit testing Stratis smart contracts.
This Guards project is a light-weight toolbox which helps you to protect your public interfaces against invalid parameters being passed over.
Neo
A simple but flexible parameter validation library.
A high-performance, extensible argument validation library.
NeoSharp Virtual Machine Interop.
NEO lightwallet / blockchain API for C#. Allows you to interact with smart contracts in the NEO blockchain.
C++ Virtual Machine compatible with NEO standard.
boost_contract-vc141. Compiler: Visual Studio 2017 15.7.4.
A NEO blockchain development toolkit that does not rely on block synchronization, including transaction construction, address translation, signature, etc.
A NNS development toolkit
boost_contract-vc140. Compiler: Visual Studio 2015 Update 3.
The Schema Checker for the Consumer Schema Tool
Neo.VM