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C# Academy · Lesson

Strings & Text: immutability, interpolation, verbatim, StringBuilder, comparison

Understand string immutability, use interpolation, escape and verbatim strings, build text efficiently with StringBuilder, compare safely, and review char/Unicode basics.

Strings & Text: immutability, interpolation, verbatim, StringBuilder, comparison is a free C# Academy lesson on CoddyKit — lesson 1 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C# Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Text overview

Goal: Use strings safely and efficiently.

  • Immutability
  • Interpolation & escapes
  • Verbatim strings
  • StringBuilder
  • Comparison & culture notes

Immutability

Immutable: methods like ToUpper or Replace return new strings; originals stay the same.

using System;

public class Program
{
  public static void Main(string[] args)
  {
    string s = "hello";
    string upper = s.ToUpper();           // new string
    Console.WriteLine("s = " + s);        // hello
    Console.WriteLine("upper = " + upper);// HELLO

    string replaced = s.Replace("h", "y"); // new string
    Console.WriteLine("replaced = " + replaced);
  }
}

Interpolation & escapes

Interpolation uses $"...". Common escapes: \\n new line, \\" quote, \\\\ backslash.

using System;

public class Program
{
  public static void Main(string[] args)
  {
    string name = "Ada";
    int score = 95;

    // C# 6 string interpolation and escapes
    string msg = $"Hi {name}, score = {score}";
    string quoted = "She said \"hi\"";
    string line = "first line\nsecond line";

    Console.WriteLine(msg);
    Console.WriteLine(quoted);
    Console.WriteLine(line);
  }
}

Verbatim strings

Verbatim strings start with @: ideal for Windows paths and multi-line text.

using System;

public class Program
{
  public static void Main(string[] args)
  {
    // Verbatim string keeps backslashes and newlines as typed
    string path = @"C:\Projects\Demo\readme.txt";
    string multi = @"Line1
Line2";
    Console.WriteLine(path);
    Console.WriteLine(multi);
  }
}

StringBuilder

For many concatenations, use StringBuilder to reduce allocations and improve performance.

using System;
using System.Text;

public class Program
{
  public static void Main(string[] args)
  {
    var sb = new StringBuilder();
    for (int i = 1; i <= 3; i = i + 1)
    {
      sb.Append("Item ").Append(i).Append(", ");
    }
    string result = sb.ToString();
    Console.WriteLine(result);
  }
}

Compare & culture; char

Use StringComparison to control comparisons (e.g., OrdinalIgnoreCase). char is a UTF-16 code unit; some emojis need surrogate pairs (beyond this intro).

using System;
using System.Globalization;

public class Program
{
  public static void Main(string[] args)
  {
    string a = "file";
    string b = "FILE";

    // Case-insensitive, culture-invariant comparison
    bool same = string.Equals(a, b, StringComparison.OrdinalIgnoreCase);
    Console.WriteLine("Same (ord ignore case) = " + same);

    // Culture example: ToUpper with current culture
    string iDot = "i";
    string upper = iDot.ToUpper(CultureInfo.CurrentCulture);
    Console.WriteLine("Upper(i) in current culture = " + upper);

  }
}

Immutability meaning

Quick check: What does it mean that strings are immutable in C#?

Recap

Recap: Strings are immutable; use interpolation and escapes; prefer @ for paths; for many appends use StringBuilder; compare with StringComparison; remember char is a UTF-16 unit.

Frequently asked questions

Is the “Strings & Text: immutability, interpolation, verbatim, StringBuilder, comparison” lesson free?

Yes — the full text of “Strings & Text: immutability, interpolation, verbatim, StringBuilder, comparison” is free to read here on the web, and the C# Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C# Academy course, upgrade to CoddyKit PRO.

What will I learn in “Strings & Text: immutability, interpolation, verbatim, StringBuilder, comparison”?

Understand string immutability, use interpolation, escape and verbatim strings, build text efficiently with StringBuilder, compare safely, and review char/Unicode basics. You practise C# Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C# Academy?

No prior experience is required. C# Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 3, so you can start here or from the beginning and move at your own pace.

How long does the “Strings & Text: immutability, interpolation, verbatim, StringBuilder, comparison” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this C# Academy lesson?

Yes. Every C# Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Strings & Text: immutability, interpolation, verbatim, StringBuilder, comparison
  2. StringBuilder, comparison & culture notes
  3. char, Unicode basics, simple parsing/formatting
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