SqlHelper.cs

    public static class SqlHelper
    {
        public static object FromDbValue(object value)
        {
            if (value == DBNull.Value)
            {
                return null;
            }
            else
            {
                return value;
            }
           
        }

        public static object ToDbValue(object value)
        {
            if (value == null)
            {
                return DBNull.Value;
            }
            else
            {
                return value;
            }
        } 

        private static string connStr = ConfigurationManager.ConnectionStrings["myconnstring"].ConnectionString;

        public static int ExecuteNonQuery(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteNonQuery();
                }
            }
        }

        public static object ExecuteScalar(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteScalar();
                }
            }
        }

        public static DataTable ExecuteDataTable(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    DataSet dataset = new DataSet();
                    SqlDataAdapter apdater = new SqlDataAdapter(cmd);
                    apdater.Fill(dataset);
                    return dataset.Tables[0];
                }
            }
        }
        public static DataSet ExecuteDataSet(string sql, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    DataSet dataset = new DataSet();
                    SqlDataAdapter apdater = new SqlDataAdapter(cmd);
                    apdater.Fill(dataset);
                    return dataset;
                }
            }
        }
    }