Most of the times we have requirements of adding different client side validations on the web pages and the easiest way to achieve this in ASP.Net is to use the existing set of validator controls.
In SharePoint when we design custom webparts which takes some data as input, we might need to add some client side validations using ASP.Net validator controls, but there are a few things that always need to be taken care of while using ASP.Net validator controls within SharePoint custom webparts.
1. Within a webpart we might have more than one control triggering server side postbacks. In this case the validator controls will validate with each and every postback, but the actual need might be to only validate the form with a single postback event, let's say through the "SUBMIT" button. To avoid this, one need to set the CausesValidation property to false for all those controls causing server side postabacks where you do not want the form to get validated.
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