A string is a sequence of characters used to represent text. The string type in C# is an alias for the System.String class in the .NET Framework. Strings in C# are immutable, meaning once a string object is created, it cannot be modified. Any operation that appears to modify a string will actually create a new string.

Key Features of C# Strings

1. Immutability: Once a string is created, it cannot be changed. Any method that appears to modify a string will return a new string.

2. String Interpolation: C# supports string interpolation, allowing you to embed expressions within string literals.

3. Escape Sequences: Strings can contain special characters using escape sequences, such as \n for a new line, \t for a tab, and \\ for a backslash.

4. String Concatenation: You can concatenate strings using the + operator or String.Concat method.

5. String Methods: The String class provides numerous methods for string manipulation, including searching, replacing, and formatting.

Detailed Examples

1. Creating Strings

csharp
1string greeting = "Hello, World!";
2string emptyString = ""; // An empty string
3string multiLineString = @"This is a multi-line
4string using verbatim syntax.";

2. String Interpolation

csharp
1string name = "Alice";
2int age = 30;
3string message = $"My name is {name} and I am {age} years old.";
4Console.WriteLine(message); // Output: My name is Alice and I am 30 years old.

3. Escape Sequences

csharp
1string path = "C:\\Program Files\\MyApp"; // Using \\ to escape backslash
2string quote = "He said, \"Hello!\""; // Using \" to include quotes
3string newLine = "First Line\nSecond Line"; // Using \n for new line
4Console.WriteLine(newLine);

4. String Concatenation

csharp
1string firstName = "John";
2string lastName = "Doe";
3string fullName = firstName + " " + lastName; // Concatenation using +
4Console.WriteLine(fullName); // Output: John Doe

5. Common String Methods

csharp
1string text = "Hello, World!";
2int length = text.Length; // Gets the length of the string
3string upper = text.ToUpper(); // Converts to uppercase
4string lower = text.ToLower(); // Converts to lowercase
5bool contains = text.Contains("World"); // Checks if it contains "World"
6string replaced = text.Replace("World", "C#"); // Replaces "World" with "C#"
7string substring = text.Substring(7, 5); // Gets a substring starting at index 7, length 5
8
9Console.WriteLine(length); // Output: 13
10Console.WriteLine(upper); // Output: HELLO, WORLD!
11Console.WriteLine(lower); // Output: hello, world!
12Console.WriteLine(contains); // Output: True
13Console.WriteLine(replaced); // Output: Hello, C#!
14Console.WriteLine(substring); // Output: World

6. String Formatting

csharp
1int quantity = 5;
2double price = 19.99;
3string formatted = string.Format("You have {0} items costing {1:C}.", quantity, price);
4Console.WriteLine(formatted); // Output: You have 5 items costing $19.99.

7. Splitting and Joining Strings

csharp
1string csv = "apple,banana,cherry";
2string[] fruits = csv.Split(','); // Splits the string into an array
3string joined = string.Join(" and ", fruits); // Joins the array into a single string
4Console.WriteLine(joined); // Output: apple and banana and cherry