Top 20 NuGet helper Packages

common netfx and netstandard libarary,extensions helpers and useful utilities
ASP.NET Core tag helpers for Subresource Integrity (SRI), Referrer meta tags, OpenGraph (Facebook) and Twitter social network meta tags.
EnumUtils provides some essential enum helper methods.
The Relativity API .NET package.
A high performance micro sql helper supporting SQL Server、MySQL、PostgreSQL、SQLite
HTML Helpers service for .NET MVC Apps.
Provides math-related convenience/helper methods.
Helpers to manage data
Experience is a useful, clean and fast functions library for .NET Projects. You can find the project wiki here:
Helper for TimeZone
Contains shared dll's and managers for comman .net programming and operations.
Helper for building nice REST API
Helper for runing Stored Procedure against a Postgresql database
A set of generic helper methods and classes for .NET Framework
Personal utility class library Combinatorics,CSV,DataTable,DateTime, Dictionary,Directory,Download,Enum,Linq,Reflection,String,TupleList,GZip related methods/types
MCART .Net Standard Edition
Accessory to Persian calendar, string extensions, encryption, ip, log and rest api for .Net. You can easily use it.
A set of extension methods helpful when building unit tests. Methods include functionality for creating random data of various types, converting data types, comparing date data, searching within string arrays, etc.
A number of simple methods to test database objects and execute sql. Currently supports Microsoft SQL Server databases.