structure vs class initialization via reference diff ?

Question

Hello friends 

Below mentioned code is working good but doubt is while object reference is created to class object vs structure object .

when calling variable using refernce.variable i am getting 100 in class i.e but in structure i am getting 10 as output ??

 

Is there anything related to value & reference mechanism of structures & class respectively .

 If so can you please do explain me the internal process in depth & i hope this the the major difference when comes to class & structures :)

using System;

namespace codefile1

{

    public class ClassPoint

    {

        public int X;

        public int Y;

        public ClassPoint(int a, int b)       

        {

            X = a;

            Y = b;

        }

        public struct StructPoint

        {

            public int X;

            public int Y;

            public StructPoint(int a, int b)

            {

                X = a;

                Y = b;

            }

            public class Test

            {

              

                static void Main()

                {

                    ClassPoint a = new ClassPoint(10, 10);

                    ClassPoint b = a;

              

                    a.X = 100;

                    StructPoint c = new StructPoint(10, 10);

                    StructPoint d = c;

   

                    c.X = 100;

                    

                    Console.WriteLine( b.X.ToString() + "," + d.X );

                    Console.ReadLine();

                }

            }

        }

    }

}

Out put : 100,10

Ty for help