Simple Pattern Matching with a Switch Expression in C#

2022 Jan 06c#

Recently having learned about pattern matching in C#, I was thinking of ways to incorporate it into my code. I came across a function that seemed like a good candidate to try it on. The function takes in a string and then returns a "cleaned" version of it so that we don’t have all sorts of variants.

public static string GetCleanedName(string fruit)
{
    if (fruit.Contains("Apple"))
    {
        return "Apple";
    }
 
    if (fruit.Contains("Pear"))
    {
        return "Pear";
    }
 
    if (fruit == "Peech")
    {
        return "Peach";
    }
 
    return fruit;
}

Changing it to a switch expression made it much more concise.

public static string GetCleanedName(string fruit)
{
    fruit = fruit switch
    {
        string s when s.Contains("Apple") => "Apple",
        string s when s.Contains("Pear") => "Pear",
        "Peech" => "Peach",
        _ => fruit
    };
 
    return fruit;
}

To make it even more concise, you can turn the function into an expression statement.

public static string GetCleanedName(string fruit) =>
    fruit switch
    {
        string s when s.Contains("Apple") => "Apple",
        string s when s.Contains("Pear") => "Pear",
        "Peech" => "Peach",
        _ => fruit
    };

In action, you would have something like this:

using System;
using System.Collections.Generic;

class Program {
  public static void Main (string[] args) {
    
    List<string> fruits = new List<string> {"Green Apple", "Asian Pear", "Peech", "Kiwi"};

    foreach(var fruit in fruits)
    {
      Console.WriteLine($"'{fruit}' becomes '{GetCleanedName(fruit)}'.");
    }
  }

  public static string GetCleanedName(string fruit) =>
  fruit switch
    {
      string s when s.Contains("Apple") => "Apple",
      string s when s.Contains("Pear") => "Pear",
      "Peech" => "Peach",
      _ => fruit
    };

  public static string GetCleanedNameOldVersion(string fruit)
  {
    if (fruit.Contains("Apple"))
    {
      return "Apple";
    }

    if (fruit.Contains("Pear"))
    {
      return "Pear";
    }

    if (fruit == "Peech")
    {
      return "Peach";
    }

    return fruit;
  }
}