How can i check for duplicate list in SharePoint using power app?

Question

[How can i check for duplicate list in SharePoint using power app][1]s.

(Note : it is not a SharePoint list form.)

Event                                      EmailEmail

SharepointSaturday               [email protected]

Azure boot camp                    [email protected]

On click of submit ,user shouldn't able to register to the same event again.So how can i check this on click of submit button.

Appreciate your help.

I have two list :

1:Registration list : where i store/create the items on submit of button in powerapps

2: Events list : is source list ,where lookup Events column in powerapps.

Answer 1

Take a look at the Filter() function. If your data source is Registration, and you want to check if a duplicate exists for a given event of event_id, and email of email then you could do something like

Filter(Registartion,event_id=event_id,email=email)

If there are any results then you know not add a new one. You can check the length of the returned array using CountRows() function

Answer 2

something like this and prevent the submit function based on your condition.

If(CountRows(Filter(DataSource,Name = "Value1")) > 0,"Exist","Does Not Exist")

detailed expression like below

If(CountRows(Filter(DataSource,Name = "Value1")) > 0, Notify("You do not have the permission to submit a record.", NotificationType.Error ),SubmitForm(EditForm1))