C# Static Classes

Summary: in this tutorial, you’ll learn about the C# static classes and how to use them to define utility classes.

Introduction to C# static classes

A static class is a class that cannot be instantiated. Typically, you use a static class to group members that are specific to a class, not an instance of the class.

A common use of a static class is to create a utility class that contains a set of methods and values like the Math library.

A static class has the following characteristics:

• A static class declaration needs to have the static keyword.
• A static class has only static members including static fields, properties, and methods.
• A static class cannot have any instance constructor but can have a static constructor.
• A static class is implicitly sealed. Therefore, you cannot subclass it.

To access members of a static class, you use the class name and the member name.

C# static class example

Let’s see an example of using a static class to define a utility class.

First, define a static class LengthConverter:

static class LengthConverter
{
    public static double FeetToMeters(double ft) => ft / 3.28084;
    public static double MetersToFeet(double m) => m * 3.28084;

}Code language: C# (cs)

The LengthConverter static class has two static methods that convert feet to meters and vice versa.

Second, use the LengthConverter class:

// Program.cs
double feet, meters;

// feet to meters
feet = 100;
meters = LengthConverter.FeetToMeters(feet);

Console.WriteLine($"{feet}ft = {meters:0.##}m");

// meters to feet
meters = 10;
feet = LengthConverter.MetersToFeet(meters);

Console.WriteLine($"{meters}m = {feet:0.##}ft");Code language: C# (cs)

Output:

100ft = 30.48m
10m = 32.81ftCode language: plaintext (plaintext)

Starting from C# 6, you can access members of a static class without the class if you have a using static directive. For example:

// Program.cs
using static LengthConverter;

double feet, meters;

// feet to meters
feet = 100;
meters = FeetToMeters(feet);

Console.WriteLine($"{feet}ft = {meters:0.##}m");

// meters to feet
meters = 10;
feet = MetersToFeet(meters);

Console.WriteLine($"{meters}m = {feet:0.##}ft");Code language: C# (cs)

Summary

• A static class cannot be instantiated and subclassed.
• A static class only has static members.
• Use a static class to define a utility class.