C# nullable values, patterns, and switch expressions

A value type such as int cannot normally be null. int? is a nullable int that either holds a value or is null. HasValue tests which, and the null-coalescing operator ?? supplies a default. The null-conditional operator ?. stops and gives null if the object is null, so text?.Length is null for a null string instead of throwing.

using System;
using System.Globalization;

class Program {
  static (int Min, int Max) MinMax(int[] values) {
    int min = values[0], max = values[0];
    foreach (int v in values) {
      if (v < min) min = v;
      if (v > max) max = v;
    }
    return (min, max);
  }

  static void Main() {
    int? maybe = null;
    Console.WriteLine(maybe.HasValue + " " + (maybe ?? -1));
    string text = null;
    Console.WriteLine(text?.Length ?? 0);

    object[] things = { 42, 7, "hello", 3.5, null, new[] { 1, 2, 3 } };
    foreach (object thing in things) {
      string description = thing switch {
        int n when n > 40 => "big int " + n,
        int n => "int " + n,
        string s => "string of length " + s.Length,
        double x => "double " + x.ToString(CultureInfo.InvariantCulture),
        null => "null",
        int[] array => "array with " + array.Length + " items",
        _ => "something else",
      };
      Console.WriteLine(description);
    }

    var (min, max) = MinMax(new[] { 4, 9, 2, 7 });
    Console.WriteLine(min + " " + max);
  }
}

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