MAUI: Issue with deleteing the last item from ObservableCollection

Question

MAUI: Issue with deleteing the last item from ObservableCollection

Sreejith Sreenivasan 1,001

I am using an ObservableCollection saving comments. When I delete a comment, I will fetch the deleted comment id and delete that comment from the ObservableCollection.

My Problem is if I delete the last comment all the previous comments are vanishing from the UI and showing only the initial comment. When I reopen the page or delete any other comment the vanished previous comments are coming back.

My Code:

foreach (var item in customerCommentList)
{
	if (item.parentComment.supportItemComments.commentId == deleteCommentId)
	{
		customerCommentList.Remove(item);
		break;
	}
}

Here customerCommentList is the collection and from that I removing the data. Is there any issue in deleting an item from the collection? Is there any known issue in net 7.0?

Screen recorder video uploaded here and here to understand the issue.

I have created a demo project and added the same logic on it and on demo it is working fine. But on the main project this logic breaks, demo is uploaded here.

Anonymous

2024-03-18T07:05:21.9733333+00:00

Do you use Listview in your project? If so, you can try to use CollectionView to make a test.
Sreejith Sreenivasan 1,001 Reputation points

2024-03-18T11:35:39.2766667+00:00

@Leon Lu (Shanghai Wicresoft Co,.Ltd.)

Yes we are using listview and collectionview. Could you please check the demo project shared? And can you show me the sample codes with refreshview?
Anonymous

2024-03-19T08:34:30.82+00:00

Could you please check the demo project shared?

Yes, I check it, when I delete it, it works.

can you show me the sample codes with refreshview?

Do you want to add refreshview in the demo to make a test?
Sreejith Sreenivasan 1,001 Reputation points

2024-03-19T09:28:13.1266667+00:00

@Anonymous

I have created a real demo and uploaded here. Could you please check that? Click on the last comment and check the UI, a few comments are vanishing from the UI. But If u reopen you can see the remaining comments on the UI. Click on the comment to see the delete option.
Sreejith Sreenivasan 1,001 Reputation points

2024-03-20T15:55:13.4666667+00:00

@Anonymous Hope you notice my last comment.
Anonymous

2024-03-21T08:24:59.1+00:00
Hi Sreejith Sreenivasan,

Could you minimize code to just what is needed to reproduce the problem? Then you can post code to this question. It will help us to troubleshoot this issue quickly.

As note: Guidelines for posting a quality question on Microsoft Q&A

By the way, could you share with us more details about set the ItemsSource again in the DeleteComment method when customerCommentList.Count not equals to 0. You can remove this commentlistview.ItemsSource = customerCommentList;, If it works.

if (customerCommentList.Count == 0) { commentlistview.IsVisible = false; //commentmessage_label.Text = "No Comments"; //commentmessage_label.IsVisible = true; } else { //commentlistview.ItemsSource = customerCommentList; }
Sreejith Sreenivasan 1,001 Reputation points

2024-03-21T15:33:20.09+00:00

@Anonymous

I have created a more optimized demo and uploaded here. This demo has the dummy data and if u delete any middle item , the items after that is vanishing from the UI. Could you please check that, I am stuck on this around a week.

By the way, could you share with us more details about set the ItemsSource again in the DeleteComment method when customerCommentList.Count not equals to 0. You can remove this commentlistview.ItemsSource = customerCommentList;, If it works.

I have added this section to solve this vanishing issue, without the else block also the feature will work fine.
Anonymous

2024-03-22T08:39:09.02+00:00

If you remove this line commentlistview.ItemsSource = customerCommentList;, will this issue(delete the last comment all the previous comments are vanishing from the UI) disappear?

However, you cannot remove this commentlistview.ItemsSource = customerCommentList; in the else part, right?
Sreejith Sreenivasan 1,001 Reputation points

2024-03-22T11:37:02.9433333+00:00

@Anonymous

If you remove this line commentlistview.ItemsSource = customerCommentList;, will this issue(delete the last comment all the previous comments are vanishing from the UI) disappear?

Yes, I commented that line and check at that time also same issue.

However, you cannot remove this commentlistview.ItemsSource = customerCommentList; in the else part, right?

That line of code is not required, if I remove the item from collection it will automatically reflected on the UI. I added that line of code when this vanishing issue happens, to check that will resolve the issue. But no luck. Are you able to recreate the issue on your part?
Sreejith Sreenivasan 1,001 Reputation points

2024-03-22T15:35:08.3066667+00:00

@Anonymous

I have created a more optimized demo with more findings and uploaded here.

On this demo I have added 2 pages, one is CommentPage and the other one is MainPage. On both pages I have used the same logic to show the items on the UI and delete an item from UI. On MainPage everything is working fine and on CommentsPage I am facing the same issues. On both the pages the UI is different, so I think the issue is related to the UI layouts. Unfortunately I can't trigger it out.

I suspect it is due to calling the functions from background thread, so I verified that and on both background thread and main UI thread the same issue is there.
Sreejith Sreenivasan 1,001 Reputation points

2024-04-01T08:58:19.11+00:00

@Leon Lu (Shanghai Wicresoft Co,.Ltd.) Please post it as your answer.
Anonymous

2024-04-01T09:08:19.9733333+00:00

Sreejith Sreenivasan I convert my comment to answer.

Accepted answer

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Your answer

Anonymous

2024-03-18T07:05:21.9733333+00:00

Do you use Listview in your project? If so, you can try to use CollectionView to make a test.
Sreejith Sreenivasan 1,001 Reputation points

2024-03-18T11:35:39.2766667+00:00

@Leon Lu (Shanghai Wicresoft Co,.Ltd.)

Yes we are using listview and collectionview. Could you please check the demo project shared? And can you show me the sample codes with refreshview?
Anonymous

2024-03-19T08:34:30.82+00:00

Could you please check the demo project shared?

Yes, I check it, when I delete it, it works.

can you show me the sample codes with refreshview?

Do you want to add refreshview in the demo to make a test?
Sreejith Sreenivasan 1,001 Reputation points

2024-03-19T09:28:13.1266667+00:00

@Anonymous

I have created a real demo and uploaded here. Could you please check that? Click on the last comment and check the UI, a few comments are vanishing from the UI. But If u reopen you can see the remaining comments on the UI. Click on the comment to see the delete option.
Sreejith Sreenivasan 1,001 Reputation points

2024-03-20T15:55:13.4666667+00:00

@Anonymous Hope you notice my last comment.
Anonymous

2024-03-21T08:24:59.1+00:00

Hi Sreejith Sreenivasan,

Could you minimize code to just what is needed to reproduce the problem? Then you can post code to this question. It will help us to troubleshoot this issue quickly.

As note: Guidelines for posting a quality question on Microsoft Q&A

By the way, could you share with us more details about set the ItemsSource again in the DeleteComment method when customerCommentList.Count not equals to 0. You can remove this commentlistview.ItemsSource = customerCommentList;, If it works.

if (customerCommentList.Count == 0) { commentlistview.IsVisible = false; //commentmessage_label.Text = "No Comments"; //commentmessage_label.IsVisible = true; } else { //commentlistview.ItemsSource = customerCommentList; }
Sreejith Sreenivasan 1,001 Reputation points

2024-03-21T15:33:20.09+00:00

@Anonymous

I have created a more optimized demo and uploaded here. This demo has the dummy data and if u delete any middle item , the items after that is vanishing from the UI. Could you please check that, I am stuck on this around a week.

By the way, could you share with us more details about set the ItemsSource again in the DeleteComment method when customerCommentList.Count not equals to 0. You can remove this commentlistview.ItemsSource = customerCommentList;, If it works.

I have added this section to solve this vanishing issue, without the else block also the feature will work fine.
Anonymous

2024-03-22T08:39:09.02+00:00

If you remove this line commentlistview.ItemsSource = customerCommentList;, will this issue(delete the last comment all the previous comments are vanishing from the UI) disappear?

However, you cannot remove this commentlistview.ItemsSource = customerCommentList; in the else part, right?
Sreejith Sreenivasan 1,001 Reputation points

2024-03-22T11:37:02.9433333+00:00

@Anonymous

If you remove this line commentlistview.ItemsSource = customerCommentList;, will this issue(delete the last comment all the previous comments are vanishing from the UI) disappear?

Yes, I commented that line and check at that time also same issue.

However, you cannot remove this commentlistview.ItemsSource = customerCommentList; in the else part, right?

That line of code is not required, if I remove the item from collection it will automatically reflected on the UI. I added that line of code when this vanishing issue happens, to check that will resolve the issue. But no luck. Are you able to recreate the issue on your part?
Sreejith Sreenivasan 1,001 Reputation points

2024-03-22T15:35:08.3066667+00:00

@Anonymous

I have created a more optimized demo with more findings and uploaded here.

On this demo I have added 2 pages, one is CommentPage and the other one is MainPage. On both pages I have used the same logic to show the items on the UI and delete an item from UI. On MainPage everything is working fine and on CommentsPage I am facing the same issues. On both the pages the UI is different, so I think the issue is related to the UI layouts. Unfortunately I can't trigger it out.

I suspect it is due to calling the functions from background thread, so I verified that and on both background thread and main UI thread the same issue is there.
Sreejith Sreenivasan 1,001 Reputation points

2024-04-01T08:58:19.11+00:00

@Leon Lu (Shanghai Wicresoft Co,.Ltd.) Please post it as your answer.
Anonymous

2024-04-01T09:08:19.9733333+00:00

Sreejith Sreenivasan I convert my comment to answer.

Answer 1

Anonymous

Please add CachingStrategy="RecycleElementAndDataTemplate" in the <ListView>. This issue is related to listview recycle policy. For more details, please see ListView cache data

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MAUI: Issue with deleteing the last item from ObservableCollection

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