An object reference is required for the nonstatic field method or property in c#

In this Example : Don't make your method (GetObject) static. It doesn't need to be static and it prevents you from using any non-static properties (like testobj). 

However if you need a method to be static, than it should not call the non-static members directly. Because the non-static member variables of a class always belong to an object.

If a method is static than non static members / properties cannot be accessed directly. otherwise create an instance to access non-static members or make the members as static. Else it will throw an error saying "an object reference is required for the nonstatic field method or property in c#" 

using System;

using System.Collections.Generic;

using System.Linq;

using System.Web;

namespace WebApplication1

{

    public class Singleton

    {

        protected static Singleton _obj;

        private Singleton()

        {

        }

        public static Singleton GetObject()

        {

            if (_obj == null)

            {

                _obj = new Singleton();

            }

            return _obj;

        }

        public void Print(string s)

        {

            Console.WriteLine(s);

        }

    }

}

If static is removed than it errors out as mentioned. Because it cannot access an instance variable.

Static Method in C#

static public int Add(int x, int y)    { 

       int result = x + y;       return result;    }//END   Add

static means that the function is not class instance dependent. So you can call it without needing to create a class instance of Program class.

or you should create in instance of your Program class, and then call Add on this instance. Like so:

 Program prog = new Program()  prog.Add(5,10);

  

Example:

namespace ConsoleApplication2

{

    class Program

    {

        

        static void Main(string[] args)

        {

            Console.WriteLine("Enter operand 1");

            int a = Convert.ToInt32(Console.ReadLine());

            Console.WriteLine("Enter operand 2");

            int b = Convert.ToInt32(Console.ReadLine());

            //Program add1 = new Program();

           

           Console.WriteLine(Program.add(a,b)); 

            

        }

        static public int add(int x, int y)

        {

            int c = x + y;

            return c;

        }

    }

}