C# class uses in classes wht it dosent work : I have class for connection to Database 
   
    namespace DamianWprawka
    {
        class SQLcon
        {
            static SqlConnection konekt = new SqlConnection();
            public SQLcon()
            {
                konekt.ConnectionString = "Data Source=.\\sqlexpress;" + "Initial Catalog=PRACA;" + "User id=sa;" + "Password=xxXXxx;";
            }
            void open()
            {
                konekt.Open();
            }
            void close()
            {
                konekt.Close();
            }
        }
    }

And other for query like insert, update, delete, dwonloadData itp:

       namespace DamianWprawka
        {
            class SQLquerry
            {
                SQLcon SQLcnn = new SQLcon();
                
                public void PobierzPracownik
                {
                   SQLcnn.Open();
                }
            }
        }

Why i can't call SQLcnn.Open(); i try with static field/class and i can only use it normaly in Main. I know i can do connection and querry in one class but i want understand this mistery for future. 