how to retrieve specific row from database in gridview?

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 Dropdownlist_gridview { public partial class _Default : System.Web.UI.Page { string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString; SqlCommand com; SqlDataAdapter sqlda; DataSet ds; string str; protected void Page_Load(object sender, EventArgs e) { SqlConnection con = new SqlConnection(strConnString); if (!IsPostBack) { DropDownList1.Items.Add("Choose Id"); con.Open(); str = "select * from employee"; com = new SqlCommand(str, con); SqlDataReader reader = com.ExecuteReader(); while (reader.Read()) { DropDownList1.Items.Add(reader["empid"].ToString()); } reader.Close(); con.Close(); } } protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) { SqlConnection con = new SqlConnection(strConnString); con.Open(); str = "select * from employee where empid='" + DropDownList1.SelectedItem.Text + "'"; com = new SqlCommand(str, con); sqlda = new SqlDataAdapter(str,con); ds = new DataSet(); sqlda.Fill(ds, "employee"); GridView1.DataMember = "employee"; GridView1.DataSource = ds; GridView1.DataBind(); con.Close(); } } }