Strings & Arrays

string name = "  ada lovelace  ";
name.Trim();                        // result thrown away!
Console.WriteLine($"[{name}]");

name = name.Trim();                 // keep the new string
Console.WriteLine($"[{name}]");

string upper = name.ToUpperInvariant();
Console.WriteLine($"{name} / {upper}");

string a = "hello";
string b = a;          // both refer to the same text
a += " world";         // a now refers to a NEW string
Console.WriteLine($"a={a}, b={b}");

Console.WriteLine(name[0]);          // reading a char is fine
Console.WriteLine("abc" == "ab" + "c"); // == compares the text

string s = "order-1042,shipped,2 items";

Console.WriteLine(s.Length);
Console.WriteLine(s.IndexOf(','));
Console.WriteLine(s.IndexOf("missing"));
Console.WriteLine(s.Contains("shipped"));
Console.WriteLine(s.StartsWith("order-"));
Console.WriteLine(s.Substring(6, 4));      // start 6, length 4
Console.WriteLine(s.Replace("shipped", "delivered"));

string[] parts = s.Split(',');
Console.WriteLine($"{parts.Length} parts, status = {parts[1]}");
Console.WriteLine(string.Join(" | ", parts));

Console.WriteLine("42".PadLeft(5, '0'));
Console.WriteLine("  hi  ".Trim().Length);
Console.WriteLine(string.IsNullOrWhiteSpace("   "));
Console.WriteLine(new string('-', 10));

using System.Text;

var sb = new StringBuilder();
sb.Append("Squares:");
for (int i = 1; i <= 5; i++)
{
    sb.Append(' ').Append(i * i);      // calls chain
}
sb.AppendLine();
sb.AppendLine("done");
sb.Insert(0, "> ");
sb.Replace("done", "DONE");

Console.Write(sb.ToString());
Console.WriteLine($"length {sb.Length}");

var csv = new StringBuilder();
string[] names = { "ana", "ben", "cy" };
for (int i = 0; i < names.Length; i++)
{
    if (i > 0) csv.Append(',');
    csv.Append(names[i]);
}
Console.WriteLine(csv);

string escaped = "C:\\logs\\app.txt";
string verbatim = @"C:\logs\app.txt";
Console.WriteLine(escaped == verbatim);
Console.WriteLine(verbatim);
Console.WriteLine(@"She said ""hi"".");

string json = """
    {
      "name": "Ada",
      "tags": ["math", "code"]
    }
    """;
Console.WriteLine(json);

string user = "ada";
int id = 7;
string sql = $"""
    SELECT * FROM users
    WHERE name = '{user}' AND id = {id}
    """;
Console.WriteLine(sql);

string a = "Apple", b = "apple";

Console.WriteLine(a == b);
Console.WriteLine(string.Equals(a, b, StringComparison.OrdinalIgnoreCase));
Console.WriteLine("report.PDF".EndsWith(".pdf", StringComparison.OrdinalIgnoreCase));

// ordinal order compares char codes: every uppercase letter sorts before lowercase
Console.WriteLine(string.Compare("Zebra", "apple", StringComparison.Ordinal) < 0);
Console.WriteLine(string.Compare("Zebra", "apple", StringComparison.OrdinalIgnoreCase) < 0);

string[] words = { "banana", "Cherry", "apple" };
Array.Sort(words, StringComparer.Ordinal);
Console.WriteLine(string.Join(", ", words));
Array.Sort(words, StringComparer.OrdinalIgnoreCase);
Console.WriteLine(string.Join(", ", words));

// a dictionary whose keys ignore case
var ages = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase) { ["Ada"] = 36 };
Console.WriteLine(ages["ADA"]);

using System.Globalization;

// The same call, two cultures, two answers.
var turkish = new CultureInfo("tr-TR");
Console.WriteLine("title".ToUpper(turkish));
Console.WriteLine("title".ToUpperInvariant());

bool sameInTurkish = string.Equals("FILE".ToLower(turkish), "file", StringComparison.Ordinal);
Console.WriteLine(sameInTurkish);

int[] empty = new int[3];              // { 0, 0, 0 }
int[] scores = { 72, 95, 60, 88 };
string[] days = new[] { "Mon", "Tue", "Wed" };

Console.WriteLine($"{empty.Length} zeros: {string.Join(",", empty)}");
Console.WriteLine($"first {scores[0]}, last {scores[scores.Length - 1]}");

scores[2] = 65;                       // elements can change, length cannot
Array.Sort(scores);
Console.WriteLine(string.Join(" ", scores));
Console.WriteLine(Array.IndexOf(scores, 88));
Console.WriteLine(Array.IndexOf(scores, 100));
Array.Reverse(days);
Console.WriteLine(string.Join(" ", days));

int total = 0;
foreach (int s in scores) total += s;
Console.WriteLine($"average {(double)total / scores.Length}");

int[,] grid =
{
    { 1, 2, 3 },
    { 4, 5, 6 },
};
Console.WriteLine($"{grid.GetLength(0)} rows x {grid.GetLength(1)} cols, Length {grid.Length}");
Console.WriteLine(grid[1, 2]);

int[][] jagged =
{
    new[] { 1 },
    new[] { 2, 3, 4 },
    new[] { 5, 6 },
};
foreach (int[] row in jagged)
    Console.WriteLine($"{row.Length}: {string.Join(" ", row)}");
Console.WriteLine(jagged[1][2]);

int[] n = { 10, 20, 30, 40, 50 };

Console.WriteLine(n[^1]);                         // last
Console.WriteLine(n[^2]);                         // second to last
Console.WriteLine(string.Join(",", n[1..3]));    // index 1 and 2
Console.WriteLine(string.Join(",", n[..2]));     // first two
Console.WriteLine(string.Join(",", n[^2..]));    // last two

string file = "report.final.pdf";
Console.WriteLine(file[..6]);
Console.WriteLine(file[(file.LastIndexOf('.') + 1)..]);

int[] slice = n[1..3];
slice[0] = 0;                                      // a copy: n is unchanged
Console.WriteLine(n[1]);

int[] data = { 1, 2, 3, 4, 5, 6 };

Span<int> middle = data.AsSpan(2, 3);   // view of 3, 4, 5
middle[0] = 30;                         // writes into data
middle.Reverse();
Console.WriteLine(string.Join(",", data));

Span<int> tail = data.AsSpan()[^2..];   // ranges work on spans too
tail.Fill(0);
Console.WriteLine(string.Join(",", data));

ReadOnlySpan<char> line = "id=42;name=ada";
int eq = line.IndexOf('=');
int semi = line.IndexOf(';');
int id = int.Parse(line[(eq + 1)..semi]);   // no substring allocated
Console.WriteLine(id + 1);