c# - How do I get customer list into a winforms app? -

i trying customer list customers.cs mainform.cs. there way list customers.cs without using sql server? want show first name under column name colfirstname , last name under column name collastname on mainform.cs. have code used mainform.cs sql customer list, required customer list without using sql connection.

customers.cs code

using system; using system.collections.generic; using system.componentmodel.dataannotations; using system.linq; using system.text; using system.threading.tasks;  namespace classproject2.data { public class customers {     public customers()     {         _customers = new list<customer>() //customer list         {             new customer(_ids.next())             {                 firstname = "bob",                 lastname = "miller"             },             new customer(_ids.next())             {                 firstname = "sue",                 lastname = "storm"             },             new customer(_ids.next())             {                 firstname = "peter",                 lastname = "parker"             }         };     }      public customer add ( customer customer )     {         if (customer == null)             throw new argumentnullexception(nameof(customer));          validator.validateobject(customer, new validationcontext(customer));          if (_customers.any(c => string.compare(c.firstname, customer.firstname, true) == 0 &&                                 string.compare(c.lastname, customer.lastname, true) == 0))             throw new argumentexception("customer exists.", nameof(customer));          customer.id = _ids.next();          _customers.add(customer);          return customer;     }      public customer ( int id )     {         return (from c in _customers                 id == c.id                 select c                ).firstordefault();     }      public ienumerable<customer> getall ()     {         return _customers;     }      public void remove(int id)     {         //verify > 0         if (id <= 0)             throw new argumentoutofrangeexception("id must > 0", nameof(id));          //find item         var item = _customers.firstordefault(i => i.id == id);          //remove         if (item != null)             _customers.remove(item);     }      private readonly list<customer> _customers;     private readonly sequence _ids = new sequence(100); } } 

code used mainform.cs

private void islinkclicked(mouseeventargs e)     {         try         {             if (e.button != mousebuttons.left) return;             datagridview.hittestinfo hti = gridcustomers.hittest(e.x, e.y);             if (hti.type == datagridviewhittesttype.cell)             {                 if (gridcustomers.rows.count > 0)                 {                     gridcustomers.currentcell = gridcustomers[hti.columnindex, hti.rowindex];                 }             }             if(hti.columnindex < 0 || hti.columnindex > gridcustomers.columncount)             {                 value = false;             }             customerform cf = new customerform();             cf.editmode = true;                             int rowindex = gridcustomers.currentcell.rowindex;             cf.id = gridcustomers.rows[rowindex].cells["colid"].value.tostring();             cf.fname = gridcustomers.rows[rowindex].cells["colfirstname"].value.tostring();             cf.lname = gridcustomers.rows[rowindex].cells["collastname"].value.tostring();             cf.show();                         }         catch (exception ex)         {             messagebox.show(ex.message);         }     } 

i don't think possible list without having connection database you're trying pull data out of.

you can dataadapter , dataset in unconnected mode in dataset can put select statement if don't want modify database , show data user