How Do I Add Add Edit,Update Buttons To A Gridview Dynamically ?

 protected void Page_Load(object sender, EventArgs e)
        {
viewgrid.AutoGenerateEditButton = true;
viewgrid.RowEditing += new GridViewEditEventHandler(viewTable_RowEditing);
}

 void viewTable_RowEditing(object sender, GridViewEditEventArgs e)
        {
          
            viewTable.EditIndex = e.NewEditIndex;
            filldata();
        }