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Syncfusion Feedback

SFListView has problems with RangedObservableCollection

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146534 Aug 7,2019 12:19 PM UTC Aug 28,2019 06:25 AM UTC Xamarin.Forms 5
Tags: SfListView
Radoslaw Kubas
Asked On August 7, 2019 12:19 PM UTC


To archive better performance I use RangedObservableCollection as SfListView.ItemsSource. It works but with some problems. Do you think is it possible to fix it?

1) NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, changedItems, startIndex)

It adds all new items to SfListView, but items are in opposite order than in changedItems. 

2) NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, removedItems)

It works only if removedItems.Count < (SfListView.ItemsSource / 2)

in the other case it throws exception:

  Message=-1 out of range 0 to 0
Parameter name: index

3) NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset);

It assumes that all items are removed, if some items exist in SfListView.ItemsSource they are hidden. 

It would be great if SfListView could fully support range add and remove, because it gives very huge performance boost. 

Best regards,

Sangeetha Raju [Syncfusion]
Replied On August 8, 2019 04:06 PM UTC

Hi Radoslaw, 
We have checked the reported query “SfListView doesn't work properly when using RangedObservableCollection” from our side. We would like to let you know that we could able to reproduce the reported issue. We have considered the reported support as a feature and added it into our feature request list. The requested feature will be available in Volume 2 SP1 Release which will be scheduled to rolled out at the end of August 2019. We will appreciate your patience until then.  
You can now track the current status of your request, review the proposed resolution timeline, and contact us for any further inquiries through this link. 
Sangeetha Raju. 

Radoslaw Kubas
Replied On August 23, 2019 07:22 AM UTC

Hello, thank you, this new feature going to be very nice.

I checked just now the latest release and it works much better, but unfortunatelly still not perfect. 

@1) NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, changedItems, startIndex)

Now it seems to work perfect. Items order is correct.

@2) NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, removedItems)

It still works if removedItems.Count < (SfListView.ItemsSource / 2). In the other case there is not Exception anymore, but result is similar like it was before after Reset. If it was for example 49 items and 45 were removed, those 4 left elements disappear as well. 

Anyway, thank you a lot for this upgrade. RangedObservableCollection is very important here :) and I believe that those issue will be addressed in coming weakly updates. 

Best regards,

Subburaj Pandian Veluchamy [Syncfusion]
Replied On August 26, 2019 12:35 PM UTC

Hi Radoslaw, 
Thank you for the update. 
We have checked the reported query from our side. We didn’t face any issues as reported. We have attached the tested sample for your reference. Please find the sample from the below link. 
Please check the sample and let us know whether the issue reproduces in our sample also? If yes, please share the details of the tested device? Else, please modify the sample based on your scenario to replicate the issue and revert to us. It will be helpful for us to check on it and provide you the solution.   
Subburaj Pandian V  

Radoslaw Kubas
Replied On August 27, 2019 08:38 AM UTC


Thank you for the example, it helps me to fine a problem (in my RangedObservableCollection implementation) and fix it. It works fine now.

As always thank you very much for you amazing support!


Subburaj Pandian Veluchamy [Syncfusion]
Replied On August 28, 2019 06:25 AM UTC

Hi Radoslaw, 
Thank you for the update. We are glad that the mentioned issue at your end with the provided solution. 
Please get in touch with us, if you would require any further assistance. 
Subburaj Pandian V   


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