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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); }}
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(); }}
linq to sql 扩展方法
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