Question

I have a linq query which fetches all records from the customer table to an observable collection as below:

customerList = new ObservableCollection<customer>(dbContext.customers);
dgRecords1.ItemsSource = customerList;

the list is bound to a datagrid.
The customer table contains many fields nearly hundred. But I display only a few fields on the datagrid. My question is

whether bringing of only selected fields from the database using linq query increase the speed the customer screen?

I need to filter and sometimes delete records from this list.

Which is the best way to select few fields into observable collection, Can someone give some sample linq queries?

Answer 1

Tips to optimize speed:

• reducing columns reduces bandwidth required
• reducing rows, but introducing paging, reduced bandwidth by much more (usually)
• turning off change-tracking and identity-management (for example ObjectTrackingEnabled in LINQ-to-SQL) will reduce overheads post-processing the data
• using a pre-compiled query can sometimes help reduce pre-processing overheads

… but frankly, when we had this problem, we solved it “once and for all” by writing “dapper”, and going old-school:

var list = connection.Query<CustomerViewModel>(
    "select {some specific cols} from Customers").ToList();

where CustomerViewModel is a simple POCO type not related to LINQ etc that just has the required values, for example:

class CustomerViewModel {
   public int Id {get;set;}
   public string Name {get;set;}
   // ...
}

This cuts out all unnecessary overheads, and is ideal when you just want to display data; additionally, the parameterization and materialization layers are very optimised (with strategy-caching, for optimum performance).