Kentico 11 Forms

I assume you're using Portal and you do want to use Forms for all other functionalities (builder, notifier, etc,)

So probably easiest to use an Event Handler docs.kentico.com/k12/.../handling-global-events

And use the BizFormItemEvents docs.kentico.com/.../reference-global-system-events

To do something custom with the data after every insert.

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Alternative could be to create a custom Web Part that would handle the whole form by itself, but that might be a lot more work...

You can use BizForm and add custom code by hook to OnBeforeSave event:

protected override void OnLoad(EventArgs e)
     {
         viewBiz.OnBeforeSave += viewBiz_OnBeforeSave;
         base.OnLoad(e);
     }

private void viewBiz_OnBeforeSave(object sender, EventArgs e)
     {
         viewBiz.StopProcessing = true; // Prevent save data
         var data = viewBiz.Data.GetValue("Photos");
        // do more ...
     }

Thank you Chu and David.