Top 4 C# Hacktoberfest2020 Projects

MaterialDesignInXamlToolkit

25 14,593 9.0 C#

Google's Material Design in XAML & WPF, for C# & VB.Net.
ClosedXML

26 4,381 9.5 C#

ClosedXML is a .NET library for reading, manipulating and writing Excel 2007+ (.xlsx, .xlsm) files. It aims to provide an intuitive and user-friendly interface to dealing with the underlying OpenXML API.

Project mention: When XML in Word Became Illegal | news.ycombinator.com | 2023-10-12

It's also country specific.
I work on Excel library and the text to number/date feature was one of less fun things to implement at least semi-correctly.
I remember my comment on the PR back then:
https://github.com/ClosedXML/ClosedXML/pull/1899

WorkOS

workos.com sponsored

The modern identity platform for B2B SaaS. The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.
CuboidalDrift

3 22 0.0 C#

A casual, fun, 3D indie game made with Unity
UtilityBelt

1 17 4.6 C#

Fun console application (by aherd2985)

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020). The latest post mention was on 2023-10-12.