Check if user already registered

Hi,
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Can someone teach show me the steps how can I check the of the user already submit the applications.
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I have create event registration form, but i don't want participants register more than 1 time.
So i want system checked the participants email and ID number as the parameter.

Use a read data action, they have a "found" event and a "not found" event, just do whatever actions you need to in there.