typed dataset probelm

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;

namespace Personal_Dataset
{
    public partial class WebForm1 : System.Web.UI.Page
    {
        SqlConnection cn;
        
         
        protected void Page_Load(object sender, EventArgs e)
        {

            cn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["PragnyaConnectionString"].ConnectionString);
            cn.Open();
            if (!IsPostBack)
            {
                bind();
            }


        }

        public void bind()
        {
            PersonalDataset dataset = new  PersonalDataset();
            PersonalDataset.PersonalDetailDataTable ds = new PersonalDataset.PersonalDetailDataTable();
            SqlDataAdapter da = new SqlDataAdapter("select  * from PersonalDetails",cn);
            da.Fill(dataset, "PersonalDetail");
             //Bind data to gridView
            grid1.DataSource = dataset.Tables ["PersonalDetail"];
            grid1.DataBind();
        }

        public void fillds()
        {
            PersonalDataset dataset = new PersonalDataset();
            SqlDataAdapter da = new SqlDataAdapter("select  * from PersonalDetails", cn);
            da.Fill(dataset, "PersonalDetails");
        }

        protected void grid1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
        {
            grid1.EditIndex = -1;
            bind();
        }

        protected void grid1_RowDeleting(object sender, GridViewDeleteEventArgs e)
        { 
        }

        protected void grid1_RowEditing(object sender, GridViewEditEventArgs e)
        {
            grid1.EditIndex = e.NewEditIndex;
            bind();
        }

        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();
            if (dataset.HasChanges())
            {
                SqlDataAdapter data_adapter = new SqlDataAdapter();
                data_adapter.TableMappings.Add("Table", "PersonalDetail");

                SqlCommandBuilder command_builder = new SqlCommandBuilder(data_adapter);

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

            }
            //PersonalDataset dataset1 = new PersonalDataset();
            //dataset1.Merge(dataset);
            //dataset.AcceptChanges();
            //dataset.PersonalDetail.AcceptChanges();
            //da.Update(dataset.Tables["PersonalDetail"]);
          
               //DataRow[] PersaldetailRow = dataset.Tables["PersonalDetail"].Select("PersonID= '" + Convert.ToInt16(personalid.Text) + "'");
            //PersaldetailRow[0]["Name"] = PName.Text;
            //PersaldetailRow[0]["City"] = City.Text;
            //PersaldetailRow[0]["Salary"] = Salary.Text;
            //dataset.Tables["PersonalDetail"].AcceptChanges();
            //da.Update(dataset.Tables ["PersonalDetail"] );
             
           
           
        }

        protected void Button1_Click(object sender, EventArgs e)
        {
            PersonalDataset dataset = new PersonalDataset();
            SqlDataAdapter da = new SqlDataAdapter();
            // Fill the dataset from DB
         string    sq = "select sum(salary)  from PersonalDetails ";
            da = new SqlDataAdapter(sq, cn);
            da.Fill(dataset);
        }
    }
}