what is static keyword in c#

static (C# Reference)

The static modifier can be used with classes, fields, methods, properties, operators, events, and constructors, but it cannot be used with indexers, destructors, or types other than classes. The static modifier on a class means that the class cannot be instantiated, and that all of its members are static. 

The following class is declared as static and contains only static methods:

static class CompanyEmployee

{

    public static void DoSomething() { /*...*/ }

    public static void DoSomethingElse() { /*...*/  }

}

A constant or type declaration is implicitly a static member.

A static member cannot be referenced through an instance. Instead, it is referenced through the type name. For example, consider the following class

While an instance of a class contains a separate copy of all instance fields of the class, there is only one copy of each static field.

It is not possible to use this to reference static methods or property accessors.

If the static keyword is applied to a class, all the members of the class must be static.

Classes and static classes may have static constructors. Static constructors are called at some point between when the program starts and the class is instantiated.

  public class Employee

{

    public string id;

    public string name;

    public Employee4()

    {

    }

    public Employee (string name, string id)

    {

        this.name = name;

        this.id = id;

    }

    public static int employeeCounter;

    public static int AddEmployee()

    {

        return ++employeeCounter;

    }

}

class MainClass : Employee

{

    static void Main()

    {

        Console.Write("Enter the employee's name: ");

        string name = Console.ReadLine();

        Console.Write("Enter the employee's ID: ");

        string id = Console.ReadLine();

        // Create and configure the employee object:

        Employee e = new Employee (name, id);

        Console.Write("Enter the current number of employees: ");

        string n = Console.ReadLine();

        Employee.employeeCounter = Int32.Parse(n);

        Employee.AddEmployee();

        // Display the new information:

        Console.WriteLine("Name: {0}", e.name);

        Console.WriteLine("ID:   {0}", e.id);

        Console.WriteLine("New Number of Employees: {0}",

                      Employee.employeeCounter);

    }

}

    /*

    Input:

    sunil

    SU643G

    10

     * 

    Sample Output:

    Enter the employee's name: Matthias Berndt

    Enter the employee's ID: SU643G

    Enter the current number of employees: 10

    Name: sunil

    ID:   SU643G

    New Number of Employees: 11

    */