// Use the following connection string.
Northwnd db = new Northwnd(@"c:\linqtest6\northwnd.mdf");

Customer newCust = new Customer();
newCust.CompanyName = "AdventureWorks Cafe";
newCust.CustomerID = "ADVCA";

// Add the customer to the Customers table.
db.Customers.InsertOnSubmit(newCust);

        protected void Button1_Click(object sender, EventArgs e)
        {
            newownerEntities1 db = new newownerEntities1(@"C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data\newowner.mdf");
            NewOwner newNewOwner = new NewOwner();           
            newNewOwner.OwnerName = Convert.ToString(TextBox2.Text);
            newNewOwner.OwnerAge = Convert.ToInt32(TextBox3.Text);
            db.NewOwner.InsertOnSubmit(newNewOwner);
        }

'System.Data.Objects.ObjectSet<ownerdog.NewOwner>' does not contain a definition for 'InsertOnSubmit' and no extension method 'InsertOnSubmit' accepting a first argument of type 'System.Data.Objects.ObjectSet<ownerdog.NewOwner>' could be found (are you missing a using directive or an assembly reference?)