why page inserts the value in database while refreshing?

Quote:

All server-side events that get fired on the post-back get fired on refresh also, but fortunately there exists one event, onsubmit, that only gets fired when there is a genuine post-back request. It is the client-side event of the form placed on your web page.

Hi,

After any event, if you refresh page then it prompt for it and if we allow it it redo last event.

Now in your situation you are inserting values in db. So on refreshing page again your db insert query fires and it insert value in db.

Now you have two ways to over come this.
1. After inserting db value redirect to same page.

e.g. //your db code
     Response.Redirect(Request.Url.AbsoluteUri);

2. In your db query, first check for value, if same value exist stop inserting in db.

Hope it helps you.
Thanks.

Check this:

Prevent-DuplicateDouble-Inserts-when-Page-is-refreshed[^]
detect-browser-refresh-to-avoid-events[^]