While GroupBy took a single collection and transformed it into multiple child collections, SelectMany flattens child collections into a single merged collection.
Let’s talk about how LINQ’s GroupBy method makes grouping data in C# easy. We’ll start basic and then go over every available overload of the GroupBy method to explore advanced use cases.
Extension methods are an integral part of modern .NET and some of .NET’s best features such as LINQ. Unfortunately, a lot of developers get intimidated by them.