castleit 

A simple dynamic expression-tree query builder. You pass it a nested collection of filters for an object, and it materializes a query capable of acting as the filter to an arbitrary collection.

A companion package for those using System.Text.Json

sharp2Js is a small library that can create javascript objects that mirror your C# POCO classes and can be easily used to generate js files using T4 templates.

A Serilog sink that writes to Azure CosmosDB. Maintained fork of an older library.