Metodlar

Salomlash("Husanboy");
Salomlash("Malika");

void Salomlash(string ism)
{
    Console.WriteLine($"Assalomu alaykum, {ism}!");
}

int natija = Qoshish(7, 5);
Console.WriteLine($"7 + 5 = {natija}");
Console.WriteLine($"Kvadrat: {Kvadrat(6)}");

int Qoshish(int a, int b)
{
    return a + b;
}

int Kvadrat(int son) => son * son;

using System.Globalization;

Console.WriteLine(Hisobla(100));
Console.WriteLine(Hisobla(100, 0.2m));
Console.WriteLine(Hisobla(100, 0.2m, 10));

string Hisobla(decimal narx, decimal chegirma = 0.1m, decimal yetkazish = 0)
{
    decimal yakuniy = narx * (1 - chegirma) + yetkazish;
    return string.Format(CultureInfo.InvariantCulture,
        "Narx {0}, chegirma {1:P0} -> {2}", narx, chegirma, yakuniy);
}

using System.Globalization;

Console.WriteLine(Hisobla(100, yetkazish: 15));
Console.WriteLine(Hisobla(narx: 200, chegirma: 0.25m));

string Hisobla(decimal narx, decimal chegirma = 0.1m, decimal yetkazish = 0)
{
    decimal yakuniy = narx * (1 - chegirma) + yetkazish;
    return string.Format(CultureInfo.InvariantCulture,
        "Yakuniy: {0}", yakuniy);
}

if (int.TryParse("42", out int son))
{
    Console.WriteLine($"O'qildi: {son}");
}

Bolish(17, 5, out int butun, out int qoldiq);
Console.WriteLine($"17 / 5 = {butun}, qoldiq {qoldiq}");

void Bolish(int a, int b, out int natija, out int qoldiq)
{
    natija = a / b;
    qoldiq = a % b;
}

int a = 5;
int b = 9;

Console.WriteLine($"Almashtirishdan oldin: a={a}, b={b}");
Almashtir(ref a, ref b);
Console.WriteLine($"Keyin:                 a={a}, b={b}");

void Almashtir(ref int x, ref int y)
{
    (x, y) = (y, x);
}

(int butun, int qoldiq) = Bolish(17, 5);
Console.WriteLine($"17 / 5 = {butun}, qoldiq {qoldiq}");

var natija = Bolish(20, 3);
Console.WriteLine($"20 / 3 = {natija.butun}, qoldiq {natija.qoldiq}");

(int butun, int qoldiq) Bolish(int a, int b) => (a / b, a % b);

Console.WriteLine(Yigindi());
Console.WriteLine(Yigindi(5));
Console.WriteLine(Yigindi(1, 2, 3, 4, 5));

int Yigindi(params int[] sonlar)
{
    int jami = 0;
    foreach (int son in sonlar)
    {
        jami += son;
    }
    return jami;
}

Console.WriteLine(Geometriya.Maydon(5));
Console.WriteLine(Geometriya.Maydon(4, 6));
Console.WriteLine(Geometriya.Maydon("kvadrat", 3));

static class Geometriya
{
    public static int Maydon(int tomon) => tomon * tomon;
    public static int Maydon(int eni, int boyi) => eni * boyi;
    public static string Maydon(string nom, int tomon) =>
        $"{nom}: {tomon * tomon}";
}

Console.WriteLine(Faktorial(5));
Console.WriteLine(Faktorial(0));

int Faktorial(int n)
{
    if (n < 0)
    {
        throw new ArgumentException("Manfiy son bo'lmasin", nameof(n));
    }

    return Hisobla(n);

    // faqat shu metod ichida ko'rinadi
    int Hisobla(int son) => son <= 1 ? 1 : son * Hisobla(son - 1);
}