I have a gridview in the asp.net page. When I insert data into the gridview the whole page will reload. How to avoid this? Here is my code

protected void AddNewCustomer(object sender, EventArgs e)
   {

       Control control = null;
       if (GridView1.FooterRow != null)
       {
           control = GridView1.FooterRow;
       }
       else
       {
           control = GridView1.Controls[0].Controls[0];
       }
       string SlNo = (control.FindControl("txtSlNo") as TextBox).Text;
       string Code = (control.FindControl("txtcode") as TextBox).Text;
       string details = (control.FindControl("txtdetails") as TextBox).Text;
       using (SqlConnection con = new SqlConnection(""))
       {
           using (SqlCommand cmd = new SqlCommand())
           {
               cmd.Connection = con;
               cmd.CommandType = CommandType.Text;
               cmd.CommandText = "INSERT INTO [Qtattemp] VALUES(@Code,@details,@SlNo)";
               cmd.Parameters.AddWithValue("@SlNo", SlNo);
               cmd.Parameters.AddWithValue("@Code", Code);
               cmd.Parameters.AddWithValue("@details", details);
               con.Open();
               cmd.ExecuteNonQuery();
               con.Close();
           }
       }
       Response.Redirect(Request.Url.AbsoluteUri);
   }