C# Strings

What You’ll Learn

Strings hold almost every piece of text in C#—user names, API responses, log messages, and file paths. This guide teaches how to create strings, understand immutability, join text with + and interpolation, compare safely, and use essential String methods.

Definition and Usage

In C#, a string is an instance of the System.String class (you can write the keyword string as a shorthand alias). It represents a sequence of characters used to store and manipulate text. You assign strings to variables, pass them to methods, and print them with Console.WriteLine().

The String class provides dozens of instance methods for comparing text, searching substrings, copying characters, and formatting output. Several helpers such as String.Compare(), String.Concat(), and String.Format() are static and are called on the class name.

📝 Syntax

C# offers several ways to create and work with strings:

string literal = "Hello, C#!";        // double-quoted literal
string built   = first + " " + last;   // + concatenation
string message = $"Hi, {name}!";       // interpolation
int len        = text.Length;          // Length property
char ch        = text[0];              // indexer (zero-based)
bool same      = text.Equals("Hi");      // compare content

Creating Strings

• String literals ("...") — the most common form; the runtime may intern identical literals for efficiency.
• Interpolation ($"...{var}...") — embed variables and expressions directly inside the string.
• Verbatim strings (@"...") — backslashes are literal; ideal for file paths and regex patterns.
• Raw string literals ("""...""") — multi-line text without escape sequences (C# 11+).

Calling String Methods

Instance methods use dot notation on a string variable; static methods use String:

name.Length
name.Contains("C#")
name.EndsWith(".cs")
String.Format("Hi, {0}", name)
String.Concat("Hello", ", ", "World")

Examples Gallery

Work through these five examples from basic string creation to comparison and search patterns used in real C# programs.

using System;

class StringsIntro
{
    static void Main()
    {
        string language = "C#";
        int version = 12;

        Console.WriteLine("Language: " + language);
        Console.WriteLine($"Version: {version}");
        Console.WriteLine("Ready to learn strings!");
    }
}

Language: C#
Version: 12
Ready to learn strings!

using System;

class StringLiterals
{
    static void Main()
    {
        string quote = "She said, \"Hello!\"";
        string path  = @"C:\Users\Dev\project";
        string lines = "Line 1\nLine 2";

        Console.WriteLine(quote);
        Console.WriteLine(path);
        Console.WriteLine(lines);
    }
}

She said, "Hello!"
C:\Users\Dev\project
Line 1
Line 2

using System;

class StringConcat
{
    static void Main()
    {
        string first = "Hello";
        string last  = "C#";

        string greeting = first + ", " + last + "!";
        Console.WriteLine(greeting);

        string status = String.Concat("Status: ", "Active");
        Console.WriteLine(status);

        Console.WriteLine($"{first}, {last}!");
    }
}

Hello, C#!
Status: Active
Hello, C#!

using System;

class StringMembers
{
    static void Main()
    {
        string word = "Hello";

        Console.WriteLine("Length: " + word.Length);
        Console.WriteLine("First char: " + word[0]);
        Console.WriteLine("Last char: " + word[word.Length - 1]);

        string copy = new string("Hello".ToCharArray());
        Console.WriteLine("Equals(): " + word.Equals(copy));
        Console.WriteLine("== : " + (word == copy));
        Console.WriteLine("ReferenceEquals: " + ReferenceEquals(word, copy));
    }
}

Length: 5
First char: H
Last char: o
Equals(): True
== : True
ReferenceEquals: False

using System;

class StringSplitSearch
{
    static void Main()
    {
        string csv  = "apple,banana,cherry";
        string url  = "https://codetofun.com/c-sharp/string";
        string file = "Program.cs";

        string[] tags = csv.Split(',');
        Console.WriteLine("Tag count: " + tags.Length);
        Console.WriteLine("Joined: " + string.Join(" | ", tags));

        Console.WriteLine("Has /c-sharp: " + url.Contains("/c-sharp"));
        Console.WriteLine("Is .cs file: " + file.EndsWith(".cs"));

        string report = String.Format(
            "Checked {0} items. URL match: {1}",
            tags.Length,
            url.Contains("/c-sharp")
        );
        Console.WriteLine(report);
    }
}

Tag count: 3
Joined: apple | banana | cherry
Has /c-sharp: True
Is .cs file: True
Checked 3 items. URL match: True

🚀 Common Use Cases

• User input — read names, emails, and commands from the console or web forms.
• Validation — check file extensions with EndsWith(), search paths with Contains().
• Display output — build messages with interpolation, +, or String.Format().
• Password checks — compare typed passwords with Equals() and an explicit StringComparison.
• Sorting text — order names or labels with Compare() or CompareTo().
• CSV and lists — split comma-separated values with Split(), join tags with string.Join().
• APIs and files — pass strings to JSON serializers, loggers, and file I/O methods.

📝 Notes

• Strings are immutable—assign the return value of methods like ToUpper() and Trim().
• For strings, == compares content; use ReferenceEquals() only when you need same-object identity.
• Guard against null: calling instance methods on null throws NullReferenceException. Use string.IsNullOrEmpty(text) first.
• Length counts UTF-16 code units; emoji and some symbols may use two units.
• Prefer StringBuilder over repeated + in loops for better performance.
• String methods use dot notation—text.Length, text.Contains("x")—not global functions like in PHP.

💡 Best Practices