using System;

using SomeOtherNamespace;

using name1;

using name1.name2;

​

// see: https://stackoverflow.com/a/66888084/1016343

namespace mainClass

{

    public static class mainClass

    {

        public static void Main()

        {

            var classFoo = new ClsFoo();

            var count = classFoo.Bar1() + classFoo.Bar2();

            Console.WriteLine($"count = {count}"); // output is 110

        } // main               

    } // class

} // namespace

​

namespace SomeOtherNamespace

{

    public class ClsFoo

    {

    } // class

} // namespace

​

namespace name1

{

    public static class FooExt

    {

        public static int Bar1(this ClsFoo foo)

        {

            return 10;

        } // method

    } // class

} // namespace

​

namespace name1.name2

{

    public static class FooExt

    {

        public static int Bar2(this ClsFoo foo)

        {

            return 100;

        } // method

    } // class

} // namespace