SqlHelper模板

在实际开发中，我们不会直接使用拼写SQL语句的方法进行数据库操作，而是使用参数化的方法进行数据库操作，这样做的好处很多，不仅提高了程序的健壮性，同时也避免的SQL注入的问题。在这里，笔者为初学者提供一个SQLHelper模板，希望对新手有所启发。

public static class SqlHelper
    {
        public static readonly string strConn = ConfigurationManager.ConnectionStrings["strConn"].ConnectionString;

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

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

        public static DataTable ExecuteDataTable(string cmdText, params SqlParameter[] parameters)
        {
            using (SqlConnection conn = new SqlConnection(strConn))
            {
                conn.Open();
                return ExecuteDataTable(conn, cmdText, parameters);
            }
        }
        public static DataTable ExecuteDataTable(SqlConnection conn, string cmdText, params SqlParameter[] parameters)
        {
            using (SqlCommand cmd = conn.CreateCommand())
            {
                cmd.CommandText = cmdText;
                cmd.Parameters.AddRange(parameters);
                using (SqlDataAdapter adapter = new SqlDataAdapter(cmd))
                {
                    DataTable dt = new DataTable();
                    adapter.Fill(dt);
                    return dt;
                }
            }
        }

        /// <summary>
        /// 存数据时防止为空
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static object ToDbValue(this object value)
        {
            return value == null ? DBNull.Value : value;
        }

        /// <summary>
        /// 取数据时防止为空
        /// </summary>
        /// <param name="value"></param>
        /// <returns></returns>
        public static object FromDbValue(this object value)
        {
            return value == DBNull.Value ? null : value;
        }
    }