Static and Instance class member

Static and Instance class member.cs

using System;

/* Important Static and Instance class member notes
 * 
 * !@!@ Class members = fields, methods, properties, events, indexers, constructors, !@!@
 * 
 * Static members are invoked using the class name
 * Instance members are invoked using instances(objects) of that class
 * 
 * An instance member belongs to a specific instance(object) of a class. 
 * If you have multiple objects of a class, each object will have have every instance member 
 * 
 * There will be only one copy of a static member, not matter how many instances of a class are created.
*/

class Circle
{
    //pi will be made as a static field, and will therefor be a static member
    static float _PI; /*
                                * mark as static because pi will remain static
                                * as pi remains static, we only need it to exist in 1 part of the memory
                                * and be shared by all of our future circle objects
                                * 
                                */
    private int _Radius;
    
    
    /*
     *      !@!@ static constructors are called BEFORE instance constructors are called, and even before the compiler refers to any static fields !@!@ 
     */
    
    //example of a static constructor, name must be the same as the class. static constructors are used to init static fields in a class
    static Circle()
    {
        Circle._PI = 3.1415f;
    }
    
    //create a constructor, same name as the Class
    public Circle(int Radius) //radius is the parameter
    {
        this._Radius = Radius; //'this' radius parameter to initialize the above class field
    } //we have used this constructor to initialize the Radius field

    //create method to print the area of a circle
    public static void Print() //<<-- *THIS IS A STATIC METHOD* >>--> ACCESS NOT FROM ANY FUTURE OBJECTS, BUT INSTEAD FROM THE CLASS, ex. Circle.Print()
    {
        //i'm just here for show
    }

    //create method to calculate area of a circle, and return it back
    public float CalculateArea() //<<-- *THIS IS AN INSTANCE METHOD* >>--> You'll need to create an object '\.o_o./' to access this method
    {
        return Circle._PI * this._Radius * this._Radius; // 3.14*radius^2 // Remember, _PI is not accessed with 'this' because it is a static member, 'this' refers to an instance member
    }
}

class Program
{
    static void Main(string[] args)
    {
        /*****static members are invoked by the name of the class
         *****instance members are invoked using instances(objects) of a class
         *
         *    !@!@ There will only be one copy of a static member in memory, no matter how many objects we create. !@!@
         */

        //create an object of the Circle Class, feed it an integer 
        Circle C1 = new Circle(5);

        //using the instance of C1, born of the Circle class, we call to the **INSTANCE METHOD** of this(C1) object, and store it to Area
        float Area = C1.CalculateArea();

        Console.WriteLine("Area = {0}", Area);
        Console.ReadKey();
    }
    
}