Multiple users accessing app at the same time - Update datasource issue

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Posted on by Iantaylor2050

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Hi @WarrenBelz

I have a bidding powerapp with SharePoint as the datasource. The app landing page has a gallery which looks like below where user can bid for items.

When two users access the app at the same time and bid for items, two winning bids are being created which is logically wrong.

When i access User A screen and User B screen after bidding, below screenshot is being shown which is wrong. Both cannot be winners.

May i know how to prevent this? This is the below code when user submits the bid successfully.

Bid Submission Code

If(
 IsBlank(
 LookUp(
 Bid_Transaction,
 Item_No = quickbidselected.'Item No',
 Bid_Price
 )
 ),
 Patch(
 Bid_Transaction,
 Defaults(Bid_Transaction),
 {
 'Name (Title)': Office365Users.UserProfile(User().Email).DisplayName,
 Designation: Office365Users.UserProfile(User().Email).JobTitle,
 Division: Office365Users.UserProfile(User().Email).Department,
 Bid_Price: Value(Label27_9.Text)+5,
 Bided_DateTime: Now(),
 Item_No: quickbidselected.'Item No',
 Email: User().Email,
 Item_Name: quickbidselected.'Item Name'
 }
 
	))

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Building Power Apps

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WarrenBelz 156,570 Most Valuable Professional on at

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Hi @Iantaylor2050 ,

Assuming your test here

If( IsBlank( LookUp( Bid_Transaction, Item_No = quickbidselected.'Item No', Bid_Price ) ), Patch( Bid_Transaction, Defaults(Bid_Transaction), { 'Name (Title)': Office365Users.UserProfile(User().Email).DisplayName, Designation: Office365Users.UserProfile(User().Email).JobTitle, Division: Office365Users.UserProfile(User().Email).Department, Bid_Price: Value(Label27_9.Text)+5, Bided_DateTime: Now(), Item_No: quickbidselected.'Item No', Email: User().Email, Item_Name: quickbidselected.'Item Name' } ) )

is the control (only patch if there are no bids), then that is the best you are going to do (if the bids are less than a few seconds apart, you may have an issue which I have seen many times on similar questions). If not, how is a "winning" bid decided.
Iantaylor2050 603 on at

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Hi @WarrenBelz ,

Winning Bid is decided based on the highest bid price value for that item in the Bid Transaction SharePoint list.

Since User A and User B bid Toothbrush at the same time for $286, both are shown as winners.

Bid Transaction SharePoint List

Winner Label Visible Code
If( First( SortByColumns( Filter( Bid_Transaction, Item_No = ThisItem.'Item No' && Email = User().Email ), "Bid_Price", SortOrder.Descending ) ).Bid_Price = Value(Label27_11.Text), true, false )
WarrenBelz 156,570 Most Valuable Professional on at

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@Iantaylor2050 ,

You could test for this and get the current highest bid

First( Sort( Filter( Bid_Transaction, Item_No = quickbidselected.'Item No' ), Bid_Price, SortOrder.Descending ) ).Bid_Price

and then make sure the current bid does not equal this.

Please click Accept as solution if my post helped you solve your issue. This will help others find it more readily. It also closes the item. If the content was useful in other ways, please consider giving it Thumbs Up.

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Iantaylor2050 603 on at

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Hi @WarrenBelz

I got your point. However, I want to prevent concurrent bidding at the same time.

If User A has bid for Toothbrush at $286, User B should see a popup dialog which says There is already a bid submitted by User A for $286. Your next bid value would be $286+$5=$291.

May i know how to achieve this?
WarrenBelz 156,570 Most Valuable Professional on at

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@Iantaylor2050 ,

If you go back to my first post, you cannot prevent absolute "concurrent" conflicting bids. The exact timing here depends on bandwidth / app performance and may be a few seconds. The best you can do with reliable means is a lookup before patching.

I will give you a concept to think about, but it has its dangers of false positives and difficulties handling errors (so it is not something I am recommending), but if your Lookup picked up the ID of the latest bid and wrote that to a number field in the new record, you could set that field in SharePoint as requiring unique values, the second one would fail at a SharePoint level (as I mentioned you would then have to try and handle this error and provide a message).

Please click Accept as solution if my post helped you solve your issue. This will help others find it more readily. It also closes the item. If the content was useful in other ways, please consider giving it Thumbs Up.

MVP (Business Applications) Visit my blog Practical Power Apps