VirtualQueryableCollectionView insert new item and save to database

[Deng]

Hi telerik,

I am confused how to use RadGridView with VirtualQueryableCollectionView in order for data virtualization, but some issues encountered when I insert a new item, let me clarify.

I use the below code to set datacontext of a window, 

var query = _context.Taxes.OrderBy(o => o.TaxID); //Order_Details.OrderBy(o => o.OrderID);
           var view = new VirtualQueryableCollectionView(query) {LoadSize = 10 };
           DataContext = view;

but there are some specified points, the Tax table only have 7 records, those records can show in grid correctly,but if I use blow code for inserting a new item,
           

private void Button_Click(object sender, RoutedEventArgs e)
    {
        (DataContext as VirtualQueryableCollectionView).AddNew(new Tax() { TaxCode = "45",TaxPercentage2 = 0.34f });
    }

this new item will not display in grid expect adding this statement
         

(DataContext as   VirtualQueryableCollectionView).VirtualItemCount++;

But executing this statement will refresh the collection and grid,  I don't want to do this. so my questions are
1. How can I show all records if called insert statement?
2. How to save a new records to database? 
I did this using below statements currently:
         

(DataContext as  VirtualQueryableCollectionView).Insert(0, newItem);
           context.CreateObjectSet<TValue>().AddObject(newItem);
           context.SaveChanges();

if I can add use VirtualQueryableCollectionView's AddNew/AddNewItem/Insert add a item to VirtualQueryableCollectionView and then call someone method to save it to database directly without needing executing context.CreateObjectSet<TValue>().AddObject(newItem);
? if yes, could you provide a sample project for me? thanks very much.

[Vlad]

Hello,

 The virtual collection is designed to handle mostly read-only scenarios. You can add/remove records from your source directly (in this case your Taxes table) and reload the collection when/if needed. 

Regards,
Vlad
the Telerik team

[Deng]

Thanks for your replying.  like I said , if I set VirtualItemCount = 10, but the table  only has 7 records, the RadGridView only show 7 records. if I add a new item, the new item would not show in RadGridView unless calling VirtualItemCount++ , what is I do not want. so Please tell me how to add new item and show it
 without call VirtualItemCount++ .

[Richard]

Hi Vlad,

Just reviving this thread. Are there any solution to this issue apart from setting the VirtualItemCount to a new value? As we all know, if that property changes, all other data loaded already are being reloaded which is not really ideal.

Thanks.

[Dimitrina]

Hi,

It is not possible to update just a single property's value.

You can also invoke the ResetItems() method for the virtual collection. Please note that this method will not raise Reset CollectionChange however it will set null for all the loaded items. 

Regards,
Didie
Telerik