Top 20 NuGet collections Packages

Extensions for ordered testing with Xunit. Full support for ordering at all levels - test collections, test classes and test cases. Support for AssemblyFixture including IMessageSink injection and IAsyncLifetime. Supports .NET Core 1.x, .NET Core 2.x. and .NET 4.5.2+
The C5 Generic Collection Library for C# and CLI is a comprehensive collection library supporting lists, sets, bags, dictionaries, priority queues, (FIFO) queues, and (LIFO) stacks. C5 runs on everything supporting .NET Standard 2.0: .NET Core 2.0+, .NET 4.6.1+, Mono, Xamarin, Universal Windows Plat...
FSharpx.Collections is a collection of datastructures for use with F# and C#.
Total functions made convenient for F# and C#
This has lots of common standard libraries like MVVM Helpers, New Collection Classes, Extensions, Exceptions, and cross platform converters.
The System.Collections namespace in the .NET Framework provides a number of collection types that are extremely useful for manipulating data in memory. However, some specialized implementations of ISet are not available. Iesi.Collections 4.0 for .Net 4.0 contains the LinkedHashSet (preserves inserti...
Backported read-only collection interfaces
Simple cross-platform memory mapping for .NET/Mono.
This is a .NET Standard 1.0, .NET 2.0, .NET 3.5, Silverlight 5.0 and Windows Phone Silverlight 8.0 & 8.1 backport from System.Collections.Concurrent.ConcurrentDictionary as defined in .NET Core
Extensions/adapters around read-only collection interfaces
A library containing useful data structures like Trees, Tries, Sparse Arrays, Bloom Filters and indexing tailored dictionaries.
General-purpose library for full-stack use. Provides support for Caching, Collections, Comparers, Converion, Environment, Events, Exceptions, IO, FileSystem, Lambdas, Logging, Math, Memory, Scopes, Text, Threading, Scheduling and many other aspects.
Provides numerous graph theory based Graph Collections
TeqCrate is a type-safe datatype-generic programming library for F#. It offers a type-safe and extensible way to inspect, decompose and create values for various kinds of common F# and .NET types.
Collection extensions and custom collections for .NET.
Heterogeneous collections for F#. Using heterogeneous collections, it's possible to act on arbitrary sum and product types in a generic way.
Select partial functions made to have warnings in F#
Contains specialized Dictionary implementations, that are 4x faster than the .NET default Dictionary. Breaking changes in 3.1.x - See https://github.com/Capgemini/Cauldron for more information.
Library of sparse collections and tools for working with them.
Provides a set of features making it possible to emulate C++ Variants for dotnet.