Pure magic in C# using tuples and relational patterns

2 Feb 2022 1 mins C#

As I was writing bunch of ifs today, I was thinking whether it would be possible to use pattern matching from recent versions of C#. To make things more interesting, I was comparing multiple values and it was not a simple equality. Blindly typing the code, I was very surprised Roslyn didn’t complain.

Let’s jump into the code and be amazed.

string Foo(int x, int y)
{
    return (x, y) switch
    {
        (> 32, not 3) => "foo",
        (> 40, not > 4) => "bar",
    };
}

The (x, y) tuple is matched, nothing special. But then. Not a simple match on exact values. It’s using relational patterns. Wow, I was not expecting that to work. Nice!

This is going to be another special tool in my toolbox.

Jiří Činčura is .NET, C# and Firebird expert. He focuses on data and business layers, language constructs, parallelism, databases and performance. For almost two decades he contributes to open-source, i.e. FirebirdClient. He works as a senior software engineer for Microsoft. Frequent speaker and blogger at www.tabsoverspaces.com.