Top 20 NuGet tree Packages

A BK tree implementation for fast, fuzzy string matching. Check out the code and usage instructions on the github page (see package information/project URL link).
Immutable persistent collections, algebraic sum-type aka descriminated union, Ref type and supportive extensions for performant functional programming in C#. Split from the DryIoc: https://github.com/dadhi/DryIoc
Interfaces and classes helpful in managing tree-like data structures. Part of the "Open" set of libraries.
Simple tools for working with immutable trees, developed at Stack Overflow
GladBehavior.Tree is a C#/.NET Behavior Tree (BT) implementation that supports generic contexts/agents.
This package contains the EPiServer CMSQL specific implementation.
CMS Query Language (CMSQL), is a DSL specifically designed for use in Content Management Systems to query over tree structured data.
Provides the Protocol Buffer Abstract Syntax Tree (AST) Descriptors. Note that we only furnish a subset of the AST for purposes of what we are doing.
k-Nearest Neighbors Search Algorithm, based on the RBush data structure
A Roslyn tool that for a given C# program shows the syntax factory API calls to construct its syntax tree.
This library exposes useful collection types and features, including: circular buffers, infinite sequences, pinned memory, tree composition and traversal.
Provides the Protocol Buffer Abstract Syntax Tree (AST) Descriptors. Note that we only furnish a subset of the AST for purposes of what we are doing.
QueryDesigner provides way of creating complex IQueryable filtering based on dynamic expression trees. Also includes filtering expression for collections like .Any(t=>t.Status && t.MaxSpeed>300)
Tree Traverse for Linq
Grapes it is an utility library which takes care of mapping tree-like data structures into database. Probably you want to install Brandy.Grapes.NHibernate or Brandy.Grapes.FluentNHibernate
Self balancing avl tree with Concat and Split operations.
A TreeView which supports, unlike the standard tree in WPF, multiple selection and is a little better stylable.