List is getting initialized every time I call method

Question

I am new to C#. I have a form with two text fields and a button and a data grid view. I am trying to pass data to Business Logic layer (BLL) and from there to Data logic layer (DAL) and there I am adding it to a list and returning back the list to the form and displaying on the data grid view. Problem is that every time I add a new record, previous records disappear. Looks like the previous entry in the list is overwritten. I have checked with debug that count in the list stays at 1. Thanks

Here is how I am calling BLL method from form to display on Data Grid:

   BLL_Customer bc = new BLL_Customer();
   dgvCustomer.DataSource = bc.BLL_Record_Customer(cust);

Here is the class in the BLL

 namespace BLL
 {
     public class BLL_Customer
     {

         public List<Customer> BLL_Record_Customer(Customer cr)
         {
             DAL_Customer dcust = new DAL_Customer();
             List<Customer> clist = dcust.DAL_Record_Customer(cr); 
             return clist;  // Reurning List
         }
     }

 }

and here is the class in DAL:

namespace DAL
 {

     public class DAL_Customer

     {
         List<Customer> clist = new List<Customer>();
         public List<Customer> DAL_Record_Customer(Customer cr)
         {
             clist.Add(cr);
             return clist;
         }
     }
 }

Answer 1

You are creating the class instances each time when try to add a new record.Make sure that only one instance of the classes are present inside any class.Create the instance of the class outside the function.

BLL_Customer bc = new BLL_Customer();


DAL_Customer dcust = new DAL_Customer();

Answer 2

Here's what's happening:

BLL_Customer bd = new BLL_Customer(); // Lets call this BLL_Customer #1
dgvCustomer.DataSource = bc.BLL_Record_Customer(cust); // Does what you expect

When this code is called again:

BLL_Customer bd = new BLL_Customer(); // Lets call this BLL_Customer #2

The old list and customer information is stored in BLL_Customer #1. The reference bd no longer points to #1, but to #2. To explain this with code I can clarify like this:

var bd = new BLL_Customer().BLL_Record_Customer(cust); // A List<Customer> 
bd = new BLL_Customer().BLL_Record_Customer(cust); // A new List<Customer>

Side note: Every time the class DAL_Customer is used for the first time in an application, your List<Customer> is initialized to a new value - in your case new List<Customer>() .

If you do not persist the information about Customers somehow, be it to a file, database, or some other means, every time you load your application, you'll have a new List<Customer> to contend with.