Pattern matching is a great feature first introduced in C# 7. You can use pattern matching on any data type, even on custom data types, to extract values from an expression.

Pattern matching was enhanced in C# 8, which introduced a wide array of new pattern types. It was enhanced even further in C# 9, with the addition of new relational and logical patterns. This article talks about the newly added patterns in C# 9 and how we can take advantage of them, with code examples wherever appropriate.

To work with the code examples provided in this article, you should have Visual Studio 2019 installed in your system. If you don’t already have a copy, you can download Visual Studio 2019 here.

Create a console application project in Visual Studio

First off, let’s create a .NET Core console application project in Visual Studio. Assuming Visual Studio 2019 is installed in your system, follow the steps outlined below to create a new .NET Core console application project in Visual Studio.

  1. Launch the Visual Studio IDE.
  2. Click on “Create new project.”
  3. In the “Create new project” window, select “Console App (.NET Core)” from the list of templates displayed.
  4. Click Next.
  5. In the “Configure your new project” window, specify the name and location for the new project.
  6. Click Create.

We’ll use this project to explore the new pattern matching features in C# 9 in the subsequent sections of this article.

Relational patterns in C# 9

Relational patterns enable the use of the relational operators less than <, less than or equal to <=, greater than >, and greater than or equal to >=.

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