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Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

26-Jul-22 2:25

As I said in my previous message, you need to call Refresh on the DataGridView. See Control.Refresh Method (System.Windows.Forms) | Microsoft Docs[^].

Code4Ever15-Jul-22 18:35

Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

15-Jul-22 18:35

I have the following code for getting data and paginating them inside the DataGrid:

private void dataPager_OnDemandLoading(object sender, Syncfusion.UI.Xaml.Controls.DataPager.OnDemandLoadingEventArgs args)
{
    List<Equipment> data;
    using (var _sqliteContext = new SQLiteContext())
    {
        data = _sqliteContext.Equipments.Include(x => x.CostCenter).Skip(args.StartIndex).Take(args.PageSize).ToList();
    }
    dataPager.LoadDynamicItems(args.StartIndex, data);
    //resetting cache for all pages.
    (dataPager.PagedSource as PagedCollectionView).ResetCache();
}

Now, I want to use background worker to do calculation in an another thread. I make the following changes:

private void dataPager_OnDemandLoading(object sender, Syncfusion.UI.Xaml.Controls.DataPager.OnDemandLoadingEventArgs args)
        {
            BackgroundWorker worker = new BackgroundWorker();
            worker.WorkerReportsProgress = false;

            worker.DoWork += worker_DoWork;
            worker.RunWorkerAsync();

        }

void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            List<Equipment> data;
            using (var _sqliteContext = new SQLiteContext())
            {
                data = _sqliteContext.Equipments.Include(x => x.CostCenter).Skip(args.StartIndex).Take(args.PageSize).ToList();
            }
            dataPager.LoadDynamicItems(args.StartIndex, data);
            //resetting cache for all pages.
            (dataPager.PagedSource as PagedCollectionView).ResetCache();
        }

But, worker_DoWork does not have any overload. I cannot pass args to worker_DoWork
How can I solve it?

OriginalGriff15-Jul-22 19:45

OriginalGriff

15-Jul-22 19:45

The DoWorkEventArgs class includes an Argument Property[^]
You can set that to an instance of any class (or struct) to pass whatever you need in.

It also contains a Result[^] property for passing completed data back to the caller via the RunWorkerCompleted Event[^]

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Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

Code4Ever15-Jul-22 19:50

Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

15-Jul-22 19:50

Is it possible to pass more than one instance of any class? Do I need to use List<t> in this case?

OriginalGriff15-Jul-22 20:00

OriginalGriff

15-Jul-22 20:00

You can use any object - so an int, a MyClass, a collection of IEnumerable objects, an array ... literally anything you need to.

Just be aware that you are multithreaded so you need to ensure thread safety if the argument data is going to be even looked at by two different threads, and that Control derived classes can only be accessed from the thread that created them (the UI thread).
But you almost certainly knew that ... I added it for those other readers who are just getting started with threading.

Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

Code4Ever15-Jul-22 19:52

Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

15-Jul-22 19:52

I used the following code for getting data from SQLite:

private void dataPager_OnDemandLoading(object sender, Syncfusion.UI.Xaml.Controls.DataPager.OnDemandLoadingEventArgs args)
        {
            List<int> list = new List<int>()
            {
                int.Parse(args.StartIndex.ToString()),
                int.Parse(args.PageSize.ToString())
            };

            BackgroundWorker worker = new BackgroundWorker();
            worker.WorkerReportsProgress = false;

            worker.DoWork += worker_DoWork;
            worker.RunWorkerAsync(list);
        }

        void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            List<int> value = (List<int>)e.Argument;
            List<Equipment> data;
            using (var _sqliteContext = new SQLiteContext())
            {
                data = _sqliteContext.Equipments.Include(x => x.CostCenter).Skip(value[0]).Take(value[1]).ToList();
            }
            this.Dispatcher.Invoke(() =>
            {
                dataPager.LoadDynamicItems(value[0], data);
                //resetting cache for all pages.
                (dataPager.PagedSource as PagedCollectionView).ResetCache();
            });
        }

There is no runtime error but the table in the UI is empty.

OriginalGriff15-Jul-22 20:02

OriginalGriff

15-Jul-22 20:02

Start with the debugger and see what data contains before you start the Invoke.

Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

Code4Ever15-Jul-22 20:04

Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

15-Jul-22 20:04

I debugged. Before Dispatcher.Invoke, the data is full of 50 records. But something happens in Dispatcher.Invoke and prevent data to be shown in the UI.

modified 16-Jul-22 2:16am.

Richard Andrew x6417-Jul-22 4:00

Richard Andrew x64

17-Jul-22 4:00

Could it be that in worker_DoWork your variable data is going out of scope when the function ends?

The difficult we do right away...
...the impossible takes slightly longer.

Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

Gerry Schmitz16-Jul-22 5:13

Gerry Schmitz

16-Jul-22 5:13

Your BackgroundWorker is going to go out of scope; I haven't used that pattern so if it gets "busy", it will be hard to tell, if at all.

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Re: Putting event handler codes inside DoWork delegate for asynchronous multi-threaded calculations

Richard Deeming17-Jul-22 20:55

Richard Deeming

17-Jul-22 20:55

Assuming you have to call the LoadDynamicItems from within the event handler, moving the data-loading code to a background thread really won't accomplish anything. You'll still need to block in the event handler until the background thread has finished, so you'll be using two threads to do what you're currently doing with one.

You'll also potentially run into issues if you're working in a framework with a concept of a "UI thread"; the control will most likely expect the LoadDynamicItems method to be called from the UI thread, not a background thread, so you'll end up getting an exception.

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Disposing issue when trying to load data from SQLite database

Code4Ever14-Jul-22 20:22

Re: Disposing issue when trying to load data from SQLite database

14-Jul-22 20:22

I'm using Syncfusion in my WPF MVVM project. I want to add pagination to my datagrid. The following code can do this:

private void dataPager_OnDemandLoading(object sender, Syncfusion.UI.Xaml.Controls.DataPager.OnDemandLoadingEventArgs args)
        {
            using (var _sqliteContext = new SQLiteContext())
            {
                dataPager.LoadDynamicItems(args.StartIndex, _sqliteContext.Equipments.Include(x => x.CostCenter).Skip(args.StartIndex).Take(args.PageSize));
                //resetting cache for all pages.
                (dataPager.PagedSource as PagedCollectionView).ResetCache();
            }
        }

The problem is that when I run the code, the application falls into the break mode and says:

Quote:
System.ObjectDisposedException: 'Cannot access a disposed context instance. A common cause of this error is disposing of a context instance that was resolved from dependency injection and then later trying to use the same context instance elsewhere in your application. This may occur if you are calling 'Dispose' on the context instance, or wrapping it in a using statement. If you are using dependency injection, you should let the dependency injection container take care of disposing context instances.
Object name: 'SQLiteContext'.'

How can I fix it?

modified 15-Jul-22 2:28am.

Richard MacCutchan14-Jul-22 21:18

Re: Disposing issue when trying to load data from SQLite database

14-Jul-22 21:18

Code4Ever wrote:
This may occur if you are calling 'Dispose' on the context instance, or wrapping it in a using statement.

Try reworking without the using statement.

Code4Ever14-Jul-22 21:30

Could not Load type spride

14-Jul-22 21:30

Thanks. Solved using the following code rework:

private void dataPager_OnDemandLoading(object sender, Syncfusion.UI.Xaml.Controls.DataPager.OnDemandLoadingEventArgs args)
        {
            List<Equipment> data;
            using (var _sqliteContext = new SQLiteContext())
            {
                data = _sqliteContext.Equipments.Include(x => x.CostCenter).Skip(args.StartIndex).Take(args.PageSize).ToList();
            }
            dataPager.LoadDynamicItems(args.StartIndex, data);
            //resetting cache for all pages.
            (dataPager.PagedSource as PagedCollectionView).ResetCache();
        }

Luis M. Rojas7-Jul-22 4:58

Re: Could not Load type spride

7-Jul-22 4:58

I had installed freespride in my asp net core project.
in the view of the controller i have this:

Spire.Doc.Document document = new Spire.Doc.Document();

but i got this error

TypeLoadException: Could not load type 'spride' from assembly 'Spire.Pdf, Version=8.2.2.0

The component it is installed, why the error?
Thanks

Pete O'Hanlon7-Jul-22 21:39

Pete O'Hanlon

7-Jul-22 21:39

There are so many reasons that this could occur. It might rely on a version of an assembly that you have the wrong version of. You might be missing a dependency somewhere. Plus numerous other reasons. If the full stack of the error doesn't tell you (and we certainly can't from a one-line trace), use depends.exe[^] to see if you can identify missing or incorrect assemblies.

Advanced TypeScript Programming Projects

Re: Could not Load type spride

Richard MacCutchan7-Jul-22 23:29

JSDOC '@extends' is not attached to class

7-Jul-22 23:29

What is "spride" and where are you trying to load it?

Luis M. Rojas4-Jul-22 5:00

4-Jul-22 5:00

Hello,
I have a project in vs2019, actually i have the following error and i can not find the error neither in google nor in microsoft, it is says is in line 1, but i can not go to the find.

Any help?

Advanced TypeScript Programming Projects

Pete O'Hanlon4-Jul-22 5:04

Pete O'Hanlon

4-Jul-22 5:04

JSDoc indicates that this is a JavaScript/TypeScript issue and has nothing to do with C#.

Luis M. Rojas4-Jul-22 5:18

4-Jul-22 5:18

Great, I know nothing about typescript, and i did not touch (because i nothing about typescript) any code of typescript, this mean: How did a made this error if i don not kwon? o How to fix?

Thanks

Advanced TypeScript Programming Projects

Pete O'Hanlon4-Jul-22 19:55

Pete O'Hanlon

4-Jul-22 19:55

What type of project do you have here? Have you searched through your code for @extends?

Luis M. Rojas5-Jul-22 2:33

5-Jul-22 2:33

I have searched @Extends, i have it, but all are // or */ but i did not touched those files.
I even knew their exists.

I loaded the project (ASPNET CORE with C#) on a different computer and the error just disapear.
Why? I don't know

Richard MacCutchan4-Jul-22 5:49