Connection String:

public class dbcommon

{

    String str = "Data Source=P02\\SQLEXPRESS;Initial Catalog=TravelManagemnt;User Id=sa;Password=softex";

        SqlConnection con;

        SqlCommand cmd;

        public int ExeNonQry(string qry)       //insert,update,delete

        {

            try

            {

                con = new SqlConnection(str);

                con.Open();

                cmd = new SqlCommand(qry, con);

                int rs = cmd.ExecuteNonQuery();

                return rs;

            }

            catch (Exception e)

            {

                return 0;

            }

            finally

            {

                con.Close();

            }

        }

        public SqlDataReader reader(string qry)  //reading values from table using sqldatareader

        {

            try

            {

                con = new SqlConnection(str);

                con.Open();

                cmd = new SqlCommand(qry, con);

                SqlDataReader dr = cmd.ExecuteReader();

                return dr;

            }

            catch (Exception e)

            {

                return null;

            }

            finally

            {  //con is not closed for reading values from table

            }

        }

        public DataTable getTable(string qry) //reading values from table using datatable

        {

            try

            {

                con = new SqlConnection(str);

                con.Open();

                SqlDataAdapter da = new SqlDataAdapter(qry, con);

                DataTable dt = new DataTable();

                da.Fill(dt);

                return dt;

            }

            catch (Exception e)

            {

                return null;

            }

            finally

            {

            }

        }

}