C# Static Field & Property

Summary: in this tutorial, you’ll learn about the C# static field and static property.

Introduction to the C# static field

A static field is bound to a class, not an instance of the class. To declare a static field, you use the static keyword. Consider the following example.

First, define the Person class:

// Person.cs

class Person
{
    public string Name;

    public Person(string name)
    {
        Name = name;
    }
}Code language: PHP (php)

In the Person class, the Name is an instance field that is bound to an instance of the Person class.

This means that each instance of the Person class has its own Name field with a separate value.

Second, create two instances of the Person class:

// Program.cs

var p1 = new Person("John");
var p2 = new Person("Jane");

Console.WriteLine($"p1 Name: {p1.Name}");
Console.WriteLine($"p2 Name: {p2.Name}");Code language: JavaScript (javascript)

In this picture, p1 and p2 are references that refer to separate Person‘s objects with their own name fields and values.

Third, add a static field Count to Person class and initialize its value to zero:

// Person.cs

class Person
{
    public string Name;

    public static int Count = 0;

    public Person(string name)
    {
        Name = name;
    }
}Code language: PHP (php)

Unlike an instance field, the compiler creates a separate memory location to store a static field once it encounters the Person class:

To access the static field Count inside the Person class, you reference the field directly:

Count

Since the static field Count is bound to the Person class, not an instance of the class, you cannot use the this keyword to reference it. The following statement will result in an error:

this.CountCode language: JavaScript (javascript)

Fourth, increase the value of the static field Count by one in the constructor:

// Person.cs

class Person
{
    public string Name;

    public static int Count = 0;

    public Person(string name)
    {
        Name = name;

        Count++;
    }
}Code language: PHP (php)

Fifth, access a static field outside of the class using the ClassName.StaticField syntax:

// Program.cs

Console.WriteLine(Person.Count); // 0Code language: JavaScript (javascript)

Finally, create two instances of the Person class. Each statement implicitly calls the Person constructor that increases the value of the Count static field by one:

// Program.cs

Console.WriteLine($"Person count: {Person.Count}"); // 0

var p1 = new Person("John");
var p2 = new Person("Jane");

Console.WriteLine($"Person count: {Person.Count}"); // 2Code language: JavaScript (javascript)

C# static property

Like a static field, a static property is bound to a class, not any instances of the class. The following example redefines the Person class with a static property Count:

class Person
{
    public string Name;

    public static int Count { get; private set; }

    public Person(string name)
    {
        Name = name;

        Count++;
    }
}Code language: PHP (php)

In this example, the Count property has a public get accessor and a private set accessor. This means that you can change the Count property inside the class and access it from both inside and outside of the class.

Summary

• Use the static keyword to define a static field or property in a class.
• A static field or property is bound to a class, not a specific instance of the class.