Question

I know I’m having a massive derp moment here and this is probably quite easy to actually do – I have had a search around and read a few articles but i’m still struggling a little, so any feedback or pointers to useful resources would be greatly appreciated!

Anyway I have a class called PopulateDatagridViews which I have various functions in, one of which is called ExecuteSqlStatement, this function is simple enough, it initializes an SQL connection and returns a DataTable populated with the results of the SQL query. Within the same class I also have various functions that use string builders to build up SQL statements. (Not ideal, I know.)

I create a PopulateDatagridViews object in my GUI thread and use it to set various datagrid views with with the returned DataTables. For example:

dataGridViewVar.DataSource = populateDgv.GetCustomers();

Naturally a problem I’m having is that the more data to be read from the database, the longer the U.I is unresponsive. I would like to shift the process of retrieving data via the PopulateDatagridViews to a separate thread or BackgroundWorker so as prevent the main GUI thread from locking up whilst this is processed.

I realise I can create a BackgroundWorker to do this and place in the DoWork handler a call to the appropriate function within my PopulateDatagridViews.

I figure I could create a BackgroundWorker for each individual function inside my PopulateDatagridViews class, but surely there is a more efficient way to do this? I’d very much appreciate a point in the right direction on this as it’s driving me around the bend!

Additional Info: I use version 4.0 of the .Net framework.

Answer 1

I strongly suggest that you use TPL (Task Parallel Library) http://msdn.microsoft.com/en-us/library/dd537609.aspx
In your case you will create first task to pull some data and than start second task after first is completed to update UI.
I`ll try to find code that i write for similar problem.

Edit: Adding code

Task<return_type> t1 = new Task<return_type>(() =>
            {
                //do something to take some result
                return some_result; //return it
            });
            t1.Start();
            Task t2 = t1.ContinueWith((some_arg_that_represent_previous_task_obj) =>{//ContinueWith guarantees that t2 is started AFTER t1 is executed!                

                //Update your GUI here
                //if you need result from previos task:   some_arg_that_represent_previous_task_obj.Result   //Your dataset or whatever

            }, TaskScheduler.FromCurrentSynchronizationContext());  //VERY important - you must update gui from same thread that created it! (you will have cross thread exeption if you dont add TaskScheduler.FromCurrentSynchronizationContext()

Hope it helps.