Static Class and Static Class Member

Static class is basically the same as a non-static class, but there is one difference: a static class cannot be instantiated. In other words, you cannot use the new keyword to create a variable of the class type. Because there is no instance variable, you access the members of a static class by using the class name itself. For example, if you have a static class that is named UtilityClass that has a public method named MethodA, you call the method as shown in the following example:
 if you have a static class that is named PrsonalClass that has a public method named MethodA, you call the method as shown in the following example:
  
PersonalClass.MethodA

As is the case with all class types, the type information for a static class is loaded by the .NET Framework common language runtime (CLR) when the program that references the class is loaded. The program cannot specify exactly when the class is loaded. However, it is guaranteed to be loaded and to have its fields initialized and its static constructor called before the class is referenced for the first time in your program. A static constructor is only called one time, and a static class remains in memory for the lifetime of the application domain in which your program resides.

Key things about StaticClass 

1 Contains only static member

2. It is Sealed

3. Cannot be instantiated(can't create object)

4. Only contain static constructor.

Static class same as the class which have static members and a private constructor. A private constructor prevents the class from being instantiated. The advantage of using a static class is that the compiler can check to make sure that no instance members are accidentally added. The compiler will guarantee that instances of this class cannot be created.

       static class MyClass

    {  

        public static int x;            

        public static int y;           

        

        static MyClass();              //Static Constructor

        public static void disp()      

        {

            x = 20;

            y = 40;

            Console.WriteLine("Value of x={0} and y={1}", x, y);

        }       

    }

Static Member

A non-static class can contain static methods, fields, properties, or events. The static member is callable on a class even when no instance of the class has been created. The static member is always accessed by the class name, not the instance name. 

Two common uses of static fields are to keep a count of the number of objects that have been instantiated, or to store a value that must be shared among all instances.

   public class Automobile

{

    public static int NumberOfWheels = 4;

    public static int SizeOfGasTank

    {

        get

        {

            return 15;

        }

    }

    public static void Drive() { }

    public static event EventType RunOutOfGas;

    // Other non-static fields and properties...

}

Static members are initialized before the static member is accessed for the first time and before the static constructor, if there is one, is called. To access a static class member, use the name of the class instead of a variable name to specify the location of the member, as shown in the following example:

        Automobile.Drive();

        int i = Automobile.NumberOfWheels;