DotNetZip by: Dino Chiesa

DotNetZip is an easy-to-use, FAST, FREE class library and toolset for manipulating zip files or folders.

Elasticsearch.Net by: Elasticsearch Inc. and contributors

Exposes all the api endpoints but leaves you in control of building the request and response bodies. Comes with built in cluster failover/connection pooling support.

elmah by: Atif Aziz

ELMAH with initial configuration for getting started quickly. ELMAH (Error Logging Modules and Handlers) is an application-wide error logging facility that is completely pluggable. It can be dynamically added to a running ASP.NET web application, or even all ASP.NET web applications on a machine, without any need for re-compilation or re-deployment.

elmah.corelibrary by: Atif Aziz

Core library for ELMAH (Error Logging Modules and Handlers) without any configuration.

EmailValidation by: Jeffrey Stedfast

A simple (but correct) .NET class for validating email addresses. Supports mail addresses as defined in rfc5322 as well as the new Internationalized Mail Address standards (rfc653x).

EntityFramework by: Microsoft

Entity Framework 6 (EF6) is a tried and tested object-relational mapper for .NET with many years of feature development and stabilization.

EntityFramework.Migrations by: Microsoft

Legacy package, Migrations is now included in the EntityFramework package.

Enums.NET by: Tyler Brinkley

Enums.NET is a high-performance type-safe .NET enum utility library

EnyimMemcached by: Attila Kiskó

Memcached client library

EPPlus by: Jan Källman

A library to manage Excel spreadsheets, using OOXML.

ExcelNumberFormat by: ExcelNumberFormat developers

.NET library to parse ECMA-376 number format strings and format values like Excel and other spreadsheet softwares.

ExCSS by: Tyler Brinks

ExCSS is a CSS 3 parser for .NET. ExCSS makes it easy to read and parse stylesheets into a friendly object model with full LINQ support.

ExtendedNumerics.BigDecimal by: https://github.com/AdamWhiteHat

Arbitrary precision decimal class

FastEndpoints by: FastEndpoints

A light-weight REST Api framework for ASP.Net 6 and newer that implements REPR (Request-Endpoint-Response) Pattern.

FastMember by: Marc Gravell

In .NET reflection is slow... well, kinda slow. If you need access to the members of an arbitrary type, with the type and member-names known only at runtime - then it is frankly hard (especially for DLR types). This library makes such access easy and fast.

Fizzler by: Atif Aziz, Colin Ramsay

Fizzler is a W3C Selectors parser and generic selector framework for document hierarchies.

FluentScheduler by: Jim Geurts

A task scheduler that uses fluent interface to configure schedules. Useful for running cron jobs/automated tasks from your application.

FluentValidation by: Jeremy Skinner

A validation library for .NET that uses a fluent interface to construct strongly-typed validation rules.

FluentValidation.ValidatorAttribute by: Jeremy Skinner

A validation library for .NET that uses a fluent interface to construct strongly-typed validation rules.

Flurl by: Todd Menier

A fluent, portable URL builder. To make HTTP calls off the fluent chain, check out Flurl.Http.