C# 9, or C# version 9.0, was released on November 10, 2020.
@ Microsoft
C# Guide
C# Version History
What’s New In C# 9
Here are select books about C# 9.
2021-01-13
C# 9.0 Pocket Reference
Edition: 1
Authors: Joseph Albahari and Ben Albahari
Publisher: O’Reilly
ISBN: 9781098101138
Type: Book
Format: Paperback
Price: US $25
On sale @ Amazon.
Shop @ O’Reilly.
2021-03-30
C# 9.0 In A Nutshell
Edition: 1
Author: Joseph Albahari
Publisher: O’Reilly
ISBN: 9781098100964
Type: Book
Format: Paperback
Price: US $80
On sale @ Amazon.
Shop @ O’Reilly.
2021-06-22
Code Like A Pro In C#
Edition: 1
Author: Jort Rodenburg
Publisher: Manning
ISBN: 9781617298028
Type: Book
Format: Paperback
Price: US $60
On sale @ Amazon.
Shop @ Manning.
2021-09-28
C# Cookbook
Edition: 1
Authors: Joe Mayo
Publisher: O’Reilly
ISBN: 9781492093695
Type: Book
Format: Paperback
Price: US $60
On sale @ Amazon.
Shop @ O’Reilly.
Here are indicators that rank programming languages.
PopularitY of Programming Language (PYPL)
The Importance Of Being Earnest (TIOBE)
P4TE 