hiii all.How can I delete gridview data rows on button click

I have 4 textbox from which i am inserting data into gridview through a Add button.Now,I have another button say Submit on click of which i have to insert the data into database.Till here it is fine.But when i try to insert another set of data into the gridview through "Add button" ,the earlier data I inserted use to popup again along with the new data which i dont want.Now my question is how can i remove the earlier inserted data from grid view.
P.S: [Gridview.datasourse=null;gridview.databind(); is not working ] 
<script runat="server"> DataTable dt1 = new DataTable(); private void gridViewAdd() { dt1.Columns.Add("regid", typeof(string)); dt1.Columns.Add("Name", typeof(string)); dt1.Columns.Add("Address", typeof(string)); dt1.Columns.Add("emailid", typeof(string)); } protected void Pag ...