C# Strings and Text

Names, addresses, search terms, log messages, and file contents all enter programs as text. A string stores an ordered sequence. Its Length reports how many UTF-16 code units it contains, and an index such as text[0] reads one char at a zero-based position. Index zero is the first position because it is an offset of zero from the start.

An empty string, "", is a real string containing no characters. It is different from a string containing one space, " ", and different again from null, which means no string value is present. That distinction becomes important when validating input.

string code = "CSharp";

Console.WriteLine(code.Length);
Console.WriteLine(code[0]);
Console.WriteLine(code[code.Length - 1]);

6
C
p

Concatenation joins strings with +, but a long chain of text and variables becomes difficult to scan. Interpolation begins with $ and evaluates expressions inside braces. It keeps the sentence shape visible and supports numeric and date formats.

Escape sequences represent characters that would otherwise be hard to place in a quoted literal. \n starts a new line, \t inserts a tab, " represents a quote, and \ represents a backslash. Verbatim strings prefixed with @ treat backslashes literally, which is convenient for Windows paths and multi-line text, although embedded quotes are doubled.

string customer = "Omar";
int orderNumber = 27;
decimal total = 31.5m;

Console.WriteLine($"Order #{orderNumber} for {customer}: {total:0.00}");

Order #27 for Omar: 31.50

Strings are immutable. Once a particular string value exists, its characters do not change. A method such as Trim creates and returns another string. If you call rawName.Trim() without storing or using the result, rawName still includes its spaces.

Immutability makes strings safe to share, but repeatedly appending inside a large loop can create many temporary strings. StringBuilder is an alternative when constructing a large piece of text through many updates. For ordinary messages and a small number of joins, interpolation is clearer and fast enough.

The == operator compares string contents using an ordinal, case-sensitive comparison. That may be right for a code or exact identifier and wrong for a command typed by a person. A login name, file path, and human-language word can each require different comparison rules.

For simple command input, string.Equals(command, "quit", StringComparison.OrdinalIgnoreCase) makes the case rule explicit. Do not normalize culturally meaningful text with ToLower and assume every language behaves like English. Choose a StringComparison value that matches the domain.

using System;

class Program
{
  static void Main()
  {
      string command = "QUIT";

      bool shouldStop = string.Equals(
          command,
          "quit",
          StringComparison.OrdinalIgnoreCase);

      Console.WriteLine(shouldStop);
  }
}

True