static class SqlHelper            {                private static string connStr = ConfigurationManager.ConnectionStrings["dbConStr"].ConnectionString;                        //封装方法的原则：把不变的放在方法里 变化的放到参数列表中                              public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)                {                    using (SqlConnection coon = new SqlConnection(connStr))                    {                        coon.Open();                        using (SqlCommand cmd = coon.CreateCommand())                        {                            cmd.CommandText = sql;                            cmd.Parameters.AddRange(parameters);                            return cmd.ExecuteNonQuery();                        }                    }                }                        public static object ExecuteScalar(string sql, params SqlParameter[] parameters)                {                    using (SqlConnection coon = new SqlConnection(connStr))                    {                        coon.Open();                        using (SqlCommand cmd = coon.CreateCommand())                        {                            cmd.CommandText = sql;                            cmd.Parameters.AddRange(parameters);                            return cmd.ExecuteScalar();                        }                    }                }                                       //由于查询的比较小  所以 可以直接用Table                public static DataTable ExecuteDataTable(string sql, params  SqlParameter[] parameters)                {                    using (SqlConnection coon = new SqlConnection(connStr))                    {                        coon.Open();                        using (SqlCommand cmd = coon.CreateCommand())                        {                            cmd.CommandText = sql;                            cmd.Parameters.AddRange(parameters);                                    DataSet dataset = new DataSet();                            SqlDataAdapter adapter = new SqlDataAdapter(cmd);                            adapter.Fill(dataset);                            return dataset.Tables[0];                        }                    }                }