linq to sql 扩展方法

老赵的博客：http://blog.zhaojie.me/2008/02/using-translate-method-and-modify-command-text-before-query-in-linq-to-sql.html

                http://www.csharpwin.com/dotnetspace/9639r2943_2.shtml

1、DataContext扩展方法

public static class DataContextExentions

    {

        /// <summary>

        /// 打开连接

        /// </summary>

        /// <param name="dataContext"></param>

        private static void OpenConnection(this DataContext dataContext)

        {

            if (dataContext.Connection.State == ConnectionState.Closed)

            {

                dataContext.Connection.Open();

            }

        }





        /// <summary>

        /// 扩展ExecuteQuery方法 

        /// </summary>

        /// <typeparam name="T"></typeparam>

        /// <param name="dataContext"></param>

        /// <param name="query"></param>

        /// <param name="withNoLock"></param>

        /// <returns></returns>

        public static List<T> ExecuteQuery<T>(this DataContext dataContext, IQueryable query, bool withNoLock)

        {

            DbCommand command = dataContext.GetCommand(query, withNoLock);



            dataContext.OpenConnection();



            using (DbDataReader reader = command.ExecuteReader())

            {

                return dataContext.Translate<T>(reader).ToList();

            }

        }





        /// <summary>

        /// 扩展ExecuteQuery方法2

        /// </summary>

        /// <typeparam name="T"></typeparam>

        /// <param name="dataContext"></param>

        /// <param name="query"></param>

        /// <param name="withNoLock"></param>

        /// <returns></returns>

        public static List<T> ExecuteQuery<T>(this DataContext dataContext, IQueryable query)

        {

            DbCommand command = dataContext.GetCommand(query);

            dataContext.OpenConnection();



            using (DbDataReader reader = command.ExecuteReader())

            {

                return dataContext.Translate<T>(reader).ToList();

            }

        }



        /// <summary>

        /// 扩展GetCommend方法，允许设置WithNoLick

        /// </summary>

        /// <param name="dataContext"></param>

        /// <param name="query"></param>

        /// <param name="withNoLock"></param>

        /// <returns></returns>

        private static SqlCommand GetCommand(this DataContext dataContext, IQueryable query, bool withNoLock)

        {

            SqlCommand command = (SqlCommand)dataContext.GetCommand(query);



            if (withNoLock)

            {

                command.CommandText = AddWithNoLock(command.CommandText);

            }



            return command;

        }



        /// <summary>

        /// 将Sql语句修改为with nolock

        /// </summary>

        /// <param name="cmdText"></param>

        /// <returns></returns>

        private static string AddWithNoLock(string cmdText)

        {

            IEnumerable<Match> matches =

                s_withNoLockRegex.Matches(cmdText).Cast<Match>()

                .OrderByDescending(m => m.Index);

            foreach (Match m in matches)

            {

                int splitIndex = m.Index + m.Value.Length;

                cmdText =

                    cmdText.Substring(0, splitIndex) + " WITH (NOLOCK)" +

                    cmdText.Substring(splitIndex);

            }



            return cmdText;

        }



        private static Regex s_withNoLockRegex =  new Regex(@"(] AS [td+])", RegexOptions.Compiled);

    }

}

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2、DataContext扩展方法支持分页

/// <summary>

/// DataContext扩展方法

/// </summary>

public static class DataContextExtends

{

    /// <summary>

    /// ExecuteQuery方法扩展，将对象以redader方式转换为实体

    /// </summary>

    /// <typeparam name="T"></typeparam>

    /// <param name="dataContext"></param>

    /// <param name="query"></param>

    /// <returns></returns>

    public static List<T> ExecuteQuery<T>(this DataContext dataContext, IQueryable<object> query)

    {

        return ExecuteQuery<T>(dataContext, query, 1, query.Cast<T>().Count());

    }



    /// <summary>

    /// ExecuteQuery方法扩展，代表分页的

    /// </summary>

    /// <typeparam name="T"></typeparam>

    /// <param name="dataContext"></param>

    /// <param name="query"></param>

    /// <param name="pageIndex"></param>

    /// <param name="pageSize"></param>

    /// <returns></returns>

    public static List<T> ExecuteQuery<T>(this DataContext dataContext, IQueryable<object> query, int pageIndex, int pageSize)

    {

        int total = query.Count();

        int totalPages = total / pageSize;



        if (total % pageSize > 0)

            totalPages++;



        if (pageIndex > totalPages)

        {

            pageIndex = totalPages;

        }

        if (pageIndex < 1)

        {

            pageIndex = 1;

        }

        query.Skip((pageIndex - 1) * pageSize).Take(pageSize).ToList();

        DbCommand command = dataContext.GetCommand(query);

        dataContext.OpenConnection();

        using (DbDataReader reader = command.ExecuteReader())

        {

            return dataContext.Translate<T>(reader).ToList();

        }

    }

    private static void OpenConnection(this DataContext dataContext)

    {

        if (dataContext.Connection.State == ConnectionState.Closed)

            dataContext.Connection.Open();

    }



}

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