typed dataset probelm

protected void grid1_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            GridViewRow GridRow = (GridViewRow)grid1.Rows[e.RowIndex];
            LinkButton btn = (LinkButton)GridRow.FindControl("lnkEdit");
            Label personalid = (Label)GridRow.FindControl("lblpersonid");
            TextBox City = (TextBox)GridRow.FindControl("txtcity");
            TextBox Salary = (TextBox)GridRow.FindControl("txtsalary");
            TextBox PName = (TextBox)GridRow.FindControl("txtname");


            PersonalDataset dataset = new PersonalDataset();

            SqlDataAdapter da = new SqlDataAdapter("select  * from PersonalDetails", cn);
            da.Fill(dataset, "PersonalDetail");


            //PersonalDataset persondataset = new PersonalDataset();
            PersonalDataset.PersonalDetailRow personalrow = dataset.PersonalDetail.FindByPersonID(Convert.ToInt16(personalid.Text));

            personalrow.City = City.Text;
            personalrow.Name = PName.Text;
            personalrow.Salary = Convert.ToInt32(Salary.Text);
            personalrow.AcceptChanges();
            dataset.PersonalDetail.AcceptChanges();
            SqlDataAdapter data_adapter = new SqlDataAdapter();
            data_adapter.TableMappings.Add("Table", "PersonalDetail");

            SqlCommandBuilder command_builder = new SqlCommandBuilder(data_adapter);

            da.Update(dataset.Tables ["PersonalDetail"]);
}