How to access Abstract Class Method

Question

Hi

namespace nsDal
{
    public abstract class clscon
    {
        protected SqlConnection con = new SqlConnection();
        public clscon()
        {
            con.ConnectionString = ConfigurationManager.ConnectionStrings["cn"].ConnectionString;
        }
    }
}

Now i want to open connection in Web Page . How it shoul be done.

Thanks

Vulpes · Answer

As Murali said abstract classes can't be instantiated and it's good practice to make any constructor protected rather than public so you can't try and do this by mistake. If you don't supply a constructor for an abstract class then the system provides a default protected parameterless constructor which does nothing apart from calling its base class constructor. Although you need to create an instance of a class which derives from clscon in order to open the connection created in the abstract class you don't need to redeclare the protected field 'con' which will give you a compiler error saying that you're hiding the base class member and worse still will reset it to a new SqlConnection object with no associated connection string. So I'd do instead: namespace nsDal { public abstract class clscon { protected SqlConnection con = new SqlConnection(); protected clscon() { con.ConnectionString = ConfigurationManager.ConnectionStrings[cn].ConnectionString; } } public class clscon1 : clscon { public void OpenConnection() { con.Open(); } } } // code to open connection clscon1 con1 = new clscon1(); con1.OpenConnection();

Muralidharan Deenathayalan · Answer

An abstract class cannot be instantiated. The purpose of an abstract class is to provide a common definition of a base class that multiple derived classes can share. So either you need to change the abstract behaviour or inherit the clscon to other class and use it. http://www.codeproject.com/KB/cs/jmabstractclasses.aspx namespace nsDal { public abstract class clscon { protected SqlConnection con = new SqlConnection(); public clscon() { con.ConnectionString = ConfigurationManager.ConnectionStrings[cn].ConnectionString; } } public class clscon1 :clscon { protected SqlConnection con = new SqlConnection(); public clscon1() : base () { } } } HTH