Belajar C#

// program C# terkecil yang berguna:
using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Halo dari C#!");
    }
}

$ dotnet --version
9.0.100

$ dotnet new console -o halo
$ cd halo
$ dotnet run
Halo dari C#!

Console.WriteLine("Halo dari C#!");
Console.WriteLine(2 + 3);
Console.Write("Tanpa pindah baris, ");
Console.WriteLine("menyambung di sini.");

Console.Write("Namamu siapa? ");
string nama = Console.ReadLine();

Console.Write("Panjang (m) = ");
double panjang = double.Parse(Console.ReadLine());

Console.Write("Lebar (m) = ");
double lebar = double.Parse(Console.ReadLine());

Console.WriteLine($"Halo {nama}, luasnya {panjang * lebar} m2");

Console.Write("Suhu (Celsius) = ");
double celsius = double.Parse(Console.ReadLine());

double fahrenheit = celsius * 9 / 5 + 32;
Console.WriteLine($"= {fahrenheit:F1} Fahrenheit");

System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.GetCultureInfo("id-ID");
string nama = "Ari";
int umur = 17;
double tinggi = 168.5;
char kelas = 'A';
bool lulus = true;

umur = umur + 1;              // ulang tahun!

var saldo = 125000m;          // m = decimal, untuk uang
Console.WriteLine($"{nama} kelas {kelas}, umur {umur}, saldo {saldo:C0}");

double hargaA = 0.1 + 0.2;
decimal hargaB = 0.1m + 0.2m;

Console.WriteLine(hargaA);   // 0.30000000000000004
Console.WriteLine(hargaB);   // 0.3

System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.GetCultureInfo("id-ID");
Console.Write("Harga satuan = ");
decimal harga = decimal.Parse(Console.ReadLine());

Console.Write("Jumlah = ");
int jumlah = int.Parse(Console.ReadLine());

decimal total = harga * jumlah;
decimal ppn = total * 0.11m;

Console.WriteLine($"Total  : {total:C0}");
Console.WriteLine($"PPN 11%: {ppn:C0}");
Console.WriteLine($"Bayar  : {total + ppn:C0}");

int a = 7, b = 2;
Console.WriteLine(a / b);          // 3 (terpotong!)
Console.WriteLine((double)a / b);  // 3.5
Console.WriteLine(a % b);          // 1 (sisanya)

Console.Write("Nilai ujian = ");
int nilai = int.Parse(Console.ReadLine());

string predikat;
if (nilai >= 90)
{
    predikat = "A — luar biasa";
}
else if (nilai >= 80)
{
    predikat = "B — bagus";
}
else if (nilai >= 70)
{
    predikat = "C — cukup";
}
else
{
    predikat = "D — ayo remedial";
}

Console.WriteLine($"Predikatmu: {predikat}");

Console.Write("Angka = ");
int n = int.Parse(Console.ReadLine());

if (n % 2 == 0)
    Console.WriteLine($"{n} genap");
else
    Console.WriteLine($"{n} ganjil");

System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.GetCultureInfo("id-ID");
Console.Write("Umur = ");
int umur = int.Parse(Console.ReadLine());

Console.Write("Hari (kerja/akhir) = ");
string hari = Console.ReadLine();

double tiket = 50000;
if ((umur < 12 || umur >= 60) && hari == "kerja")
{
    tiket *= 0.5;   // diskon 50%: rentan usia di hari kerja
}
else if (hari == "akhir")
{
    tiket *= 0.9;   // akhir pekan selalu -10%
}

Console.WriteLine($"Tiketmu: {tiket:C0}");

string sandi = "rahasia";
int percobaan = 2;

// bersarang: dua gerbang berurutan
if (sandi == "rahasia")
{
    if (percobaan <= 3)
    {
        Console.WriteLine("Masuk!");
    }
}

// digabung: satu pertanyaan majemuk
if (sandi == "rahasia" && percobaan <= 3)
{
    Console.WriteLine("Masuk!");
}

System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.GetCultureInfo("id-ID");
Console.WriteLine("=== KAFE KODE ===");
Console.WriteLine("1. Kopi    Rp15000");
Console.WriteLine("2. Teh     Rp8000");
Console.WriteLine("3. Susu    Rp12000");
Console.Write("Pilihanmu: ");

int pilih = int.Parse(Console.ReadLine());
string menu;
int harga;

switch (pilih)
{
    case 1:
        menu = "Kopi";  harga = 15000; break;
    case 2:
        menu = "Teh";   harga = 8000;  break;
    case 3:
        menu = "Susu";  harga = 12000; break;
    default:
        menu = "-";     harga = 0;     break;
}

Console.WriteLine($"Kamu memesan {menu} ({harga:C0})");

Console.Write("Hari = ");
string hari = Console.ReadLine().ToLower();

int diskon = hari switch
{
    "senin" or "selasa" => 20,
    "jumat"             => 15,
    _                   => 0,
};

Console.WriteLine($"Diskon hari {hari}: {diskon}%");

Console.Write("Sampai angka berapa? ");
int n = int.Parse(Console.ReadLine());

int total = 0;
for (int i = 1; i <= n; i++)
{
    total += i;
}

Console.WriteLine($"Jumlah 1 sampai {n} = {total}");

for (int i = 1; i <= 10; i++)
{
    Console.WriteLine($"7 x {i,2} = {7 * i}");
}

// rata-rata dari n nilai:
Console.Write("Berapa nilai? ");
int n = int.Parse(Console.ReadLine());

double jumlah = 0;
for (int i = 1; i <= n; i++)
{
    Console.Write($"Nilai ke-{i}: ");
    jumlah += double.Parse(Console.ReadLine());
}
Console.WriteLine($"Rata-rata: {jumlah / n:F2}");

Console.Write("Tinggi segitiga: ");
int tinggi = int.Parse(Console.ReadLine());

for (int i = 1; i <= tinggi; i++)
{
    string baris = "";
    for (int j = 1; j <= i; j++)
    {
        baris += "* ";
    }
    Console.WriteLine(baris);
}

// persegi 5x5
for (int i = 1; i <= 5; i++)
{
    for (int j = 1; j <= 5; j++) Console.Write("* ");
    Console.WriteLine();
}

// tabel 5x5
for (int i = 1; i <= 5; i++)
{
    for (int j = 1; j <= 5; j++) Console.Write($"{i * j,4}");
    Console.WriteLine();
}

Console.WriteLine("Ketik angka untuk dijumlahkan, 0 untuk berhenti.");

double total = 0;
int banyak = 0;

while (true)
{
    Console.Write("> ");
    double angka = double.Parse(Console.ReadLine());

    if (angka == 0) break;

    total += angka;
    banyak++;
}

Console.WriteLine($"Total {total} dari {banyak} angka, rata-rata {total / banyak:F2}");

string pilihan;
do
{
    Console.WriteLine("[1] Saldo  [2] Setor  [3] Keluar");
    Console.Write("> ");
    pilihan = Console.ReadLine();

    if (pilihan == "1") Console.WriteLine("Saldo: Rp250.000");
    else if (pilihan == "2") Console.WriteLine("Setoran dicatat!");
}
while (pilihan != "3");

Console.WriteLine("Sampai jumpa!");

int umur;
while (true)
{
    Console.Write("Umurmu (1-120): ");
    try
    {
        umur = int.Parse(Console.ReadLine());
        if (umur >= 1 && umur <= 120) break;
        Console.WriteLine("Di luar rentang wajar, coba lagi.");
    }
    catch (FormatException)
    {
        Console.WriteLine("Itu bukan angka — angka saja ya.");
    }
}

Console.WriteLine($"Tercatat: {umur} tahun.");

System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.GetCultureInfo("id-ID");
Console.Write("Harga = ");
if (int.TryParse(Console.ReadLine(), out int harga))
{
    Console.WriteLine($"OK, {harga:C0} tercatat.");
}
else
{
    Console.WriteLine("Bukan angka yang valid.");
}

using System;

class Program
{
    static double Diskon(double harga, int persen)
    {
        return harga * persen / 100;
    }

    static string Kategori(double imt)
    {
        if (imt < 18.5) return "Kurus";
        if (imt < 25) return "Ideal";
        return "Berlebih";
    }

    static void Main()
    {
        System.Threading.Thread.CurrentThread.CurrentCulture = System.Globalization.CultureInfo.GetCultureInfo("id-ID");
        Console.Write("Harga = ");
        double harga = double.Parse(Console.ReadLine());
        double bayar = harga - Diskon(harga, 20);
        Console.WriteLine($"Setelah diskon 20%: {bayar:C0}");

        Console.Write("IMT = ");
        double imt = double.Parse(Console.ReadLine());
        Console.WriteLine($"Kategori: {Kategori(imt)}");
    }
}

using System;

class Program
{
    static void Sapa(string nama)
    {
        Console.WriteLine($"Halo, {nama}!");
    }

    static void Sapa(string nama, string gelar)
    {
        Console.WriteLine($"Halo, {gelar} {nama}!");
    }

    static (int Min, int Maks) Rentang(int a, int b)
    {
        return (Math.Min(a, b), Math.Max(a, b));
    }

    static void Main()
    {
        Sapa("Ari");
        Sapa("Ari", "Kak");
        var rentang = Rentang(42, 17);
        Console.WriteLine($"{rentang.Min} ... {rentang.Maks}");
    }
}

using System;
using System.Collections.Generic;

class Program
{
    static int Terbesar(List<int> data)
    {
        int maks = data[0];
        foreach (int n in data)
            if (n > maks) maks = n;
        return maks;
    }

    static double Rata(List<int> data)
    {
        double total = 0;
        foreach (int n in data) total += n;
        return total / data.Count;
    }

    static void Main()
    {
        List<int> nilai = new List<int> { 80, 90, 75, 95, 68 };
        foreach (int n in nilai) Console.WriteLine($"Nilai: {n}");
        Console.WriteLine($"Terbesar: {Terbesar(nilai)}");
        Console.WriteLine($"Rata-rata: {Rata(nilai):F2}");
    }
}

List<string> tugas = new List<string> { "Belajar C#", "Olahraga", "Baca buku" };

tugas.Add("Belanja mingguan");
tugas.Remove("Olahraga");

Console.WriteLine($"{tugas.Count} tugas tersisa:");
foreach (string t in tugas)
{
    Console.WriteLine($"- {t}");
}