Learn LINQ in C# here with this tutorial and follow along in Visual Studio or Visual Studio Code. LINQ is a fundamental part of C# in .NET and makes you able to chain functions together in the so-called lambda syntax and write clean code for lists, arrays and database queries.
It combines perfectly with Entity Framework or Dapper for SQL Server queries but also against other databases.
LINQ is industry standard and knowledge of it will make you attractive to get a programming job! It works just as well in .NET Core, .NET Standard and the old .NET Framework.
Go here to learn all about LINQ and improve the readability and efficiency of your code!