Working with disconnected architecture in ASP.NET

using System;
using System.Data;
public partial class Default3 : System.Web.UI.Page
{
    DataTable dt;
    protected void Page_Load(object sender, EventArgs e)
    {
        dt = new DataTable();
        // Creating columns
        dt.Columns.Add("EmployeeID", typeof(int));
        dt.Columns.Add("Name", typeof(string));        
        dt.Columns.Add("City", typeof(string));
        dt.Columns.Add("Salary", typeof(double));
        dt.Columns.Add("Department", typeof(string));
        //Adding Rows
        dt.Rows.Add(111, "Raj", "Nagpur",45000,"IT");
        dt.Rows.Add(222, "Neha", "Kanpur",20000,"Accounts");
        dt.Rows.Add(333, "Amit","New York",30000, "Management");
        dt.Rows.Add(444, "Digvijay", "Kanpur", 35000, "IT");
        dt.Rows.Add(555, "Rajesh", "Delhi", 25000, "HR");
        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
}

protected void btnAddNewRow_Click(object sender, EventArgs e)
{
        DataRow dr = dt.NewRow();
        dr["EmployeeID"] = 666;
        dr["Name"] = "Atul";
        dr["City"] = "Mumbai";
        dr["Salary"] = 12000;
        dr["Department"] = "CS";
       //Add the new row to datatable
        dt.Rows.Add(dr);        
        GridView1.DataBind();
}

Example

using System;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
public partial class Default : System.Web.UI.Page
{
    SqlConnection conn;
    SqlDataAdapter adapter;
    DataSet ds;
    protected void Page_Load(object sender, EventArgs e)
    {
        string cs = ConfigurationManager.ConnectionStrings["conString"].ConnectionString;
        try
        {
            conn = new SqlConnection(cs);
            adapter = new SqlDataAdapter("select * from tblEmps", conn);
            ds = new DataSet();
            adapter.Fill(ds);
            GridView1.DataSource = ds;
            GridView1.DataBind();
        }
        catch(Exception ex)
        {
            Label1.Text = "ERROR :: " + ex.Message;
        }
        finally
        {
            ds.Dispose();
            conn.Dispose();
        }        
    }    
}