"Relational pattern"lar haqida...

C# 9.0 dan boshlab, switchga parametr qilib berilgan qiymatni aniq qiymatlar bilanmasde malum bir diapazondigi qiymatla bilan solishtiraish uchun relational patterndan foydalanamiz:

Console.WriteLine(Classify(13));  // output: Too high
Console.WriteLine(Classify(double.NaN));  // output: Unknown
Console.WriteLine(Classify(2.4));  // output: Acceptable

static string Classify(double measurement) => measurement switch
{
    < -4.0 => "Too low",
    > 10.0 => "Too high",
    double.NaN => "Unknown",
    _ => "Acceptable",
};

Relational patterda siz <, >, <= yoki >= kabi solishtirish operatorlaridan foydalanishingiz mumkin. Relational patternning o'ng tomoni constant ifoda bo'lishi kerak.
Constant qiymat int, float, char yoki enum tipidagi bo'lishi mumkin.

Ifodaning natijasi ma'lum diapazonda ekanligini tekshirish uchun uni "conjunctive and pattern" bilan moslang :

Console.WriteLine(GetCalendarSeason(new DateTime(2021, 3, 14)));  // output: spring
Console.WriteLine(GetCalendarSeason(new DateTime(2021, 7, 19)));  // output: summer
Console.WriteLine(GetCalendarSeason(new DateTime(2021, 2, 17)));  // output: winter

static string GetCalendarSeason(DateTime date) => date.Month switch
{
    >= 3 and < 6 => "spring",
    >= 6 and < 9 => "summer",
    >= 9 and < 12 => "autumn",
    12 or (>= 1 and < 3) => "winter",
    _ => throw new ArgumentOutOfRangeException(nameof(date), $"Date with unexpected month: {date.Month}."),
};

Agar ifoda natijasi null bo'lsa yoki constant qiymatni nullable qiymatga convert qilish imkoni bo'lmasa relational pattern ifodaga mos kelmaydi.
Qo'shimcha ma'lumot olish uchun relational pattern bo'limiga qarang.