Static members, static classes and partial classes — OOP Concepts in C#

4. Static members, static classes and partial classes

BasicMediumLesson 4 of 15

csharp

public static class MathHelper                   // cannot be instantiated or inherited
{
    public static double Square(double x) => x * x;
}

public class Counter
{
    public static int Instances;                 // shared across all objects
    public Counter() => Instances++;
}

public partial class Customer { public string Name { get; set; } = ""; }   // file 1
public partial class Customer { public string Display() => Name.ToUpper(); } // file 2 (e.g. generated code)

Static members belong to the type, not to an object. Avoid mutable static state in web apps — it is shared by every request and thread.