String Manipulation

C# in Visual Studio 2026 — a hands-on guide for developers at every level.

String Basics

Strings in C# are immutable sequences of Unicode characters represented by the string type (an alias for System.String). Every operation that appears to modify a string actually creates a new one.

string s = "Hello, World!";
Console.WriteLine(s.Length);        // 13
Console.WriteLine(s.ToUpper());     // HELLO, WORLD!
Console.WriteLine(s.ToLower());     // hello, world!
Console.WriteLine(s.Replace("World", "C#")); // Hello, C#!

Useful String Methods

string text = "  Hello, C#!  ";
Console.WriteLine(text.Trim());          // "Hello, C#!"
Console.WriteLine(text.TrimStart());     // "Hello, C#!  "
Console.WriteLine(text.Contains("C#"));  // True
Console.WriteLine(text.StartsWith("  H")); // True
Console.WriteLine(text.IndexOf("C#"));   // 9
Console.WriteLine(text.Substring(2, 5));  // "Hello"

Split and Join

string csv = "apple,banana,cherry";
string[] fruits = csv.Split(',');
foreach (var f in fruits)
    Console.WriteLine(f);

string joined = string.Join(" | ", fruits);
Console.WriteLine(joined); // apple | banana | cherry

Verbatim and Raw Strings

// Verbatim string — backslashes are literal
string path = @"C:\Users\Alice\Documents";

// Raw string literal (C# 11+) — no escaping needed
string json = """
{
  "name": "Alice",
  "age": 30
}
""";

StringBuilder for Performance

When building strings in a loop, use StringBuilder to avoid creating hundreds of intermediate string objects:

using System.Text;

var sb = new StringBuilder();
for (int i = 1; i <= 5; i++)
    sb.AppendLine($"Line {i}");

Console.WriteLine(sb.ToString());