dataset is not visible in intelligence dropdownlist

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ASP.NET

ADO.NET

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;

namespace WebApplication1
{
    public partial class About : System.Web.UI.Page
    {
        string connstr = (@"server=KANHA-PC;database=asp1;integrated security=true;");
        public void grid_fill()
        {
            SqlConnection con = new SqlConnection(connstr);
            SqlDataAdapter da = new SqlDataAdapter("select * from asp", con);
            dataset ds = new dataset();
            da.Fill(ds);
            GridView1.DataSource = ds;
            GridView1.DataBind(); 
            con.Close();
            }

its showing erroe:-

Error 1 The type or namespace name 'dataset' could not be found (are you missing a using directive or an assembly reference?) c:\users\kanha\documents\visual studio 2010\projects\WebApplication1\WebApplication1\About.aspx.cs 18 13 WebApplication1

Error 2 The type or namespace name 'dataset' could not be found (are you missing a using directive or an assembly reference?) c:\users\kanha\documents\visual studio 2010\projects\WebApplication1\WebApplication1\About.aspx.cs 18 30 WebApplication1

anuone can suggest me what is the problem in my visual studio 2010.

thanx in advance
Rakesh Sharma