C#: What is the difference between struct and class in C#?

struct — value type. class — reference type.

struct:

• Value type (stack).
• Inherits from System.ValueType.
• Cannot have parameterless constructor.
• Cannot inherit (but can implement interfaces).
• No finalizer.
• Must initialize all fields.

1public struct Point {
2    public int X { get; set; }
3    public int Y { get; set; }
4}
5
6Point p1 = new Point { X = 1, Y = 2 };
7Point p2 = p1;  // Copy
8p2.X = 10;      // p1.X still 1

class:

• Reference type (heap).
• Inherits from System.Object.
• Can have parameterless constructor.
• Supports inheritance.
• Can have finalizer.

1public class Person {
2    public string Name { get; set; }
3}
4
5Person p1 = new Person { Name = "Alice" };
6Person p2 = p1;  // Copy reference
7p2.Name = "Bob"; // p1.Name also "Bob"

When to use struct:

• Small, immutable data.
• Examples: Point, Rectangle, Complex.