public static class DbFunctionUnitTestable    {        /// <summary>        /// This is for Unit Test.        /// When Running against DB ,EF will generate the SQL and ignore the implemenation        /// in this method . when calling from C#(Unit test) , will exeucte the logic below        /// </summary>        /// <param name="dt"></param>        /// <returns></returns>        [System.Data.Entity.DbFunction("Edm", "TruncateTime")]        public static DateTime? TruncateTime(DateTime? dt)        {            if (dt.HasValue)            {                return dt.Value.Date;            }            return null;        }    }2. 在運行時，如果是LINQ to ENTITY，EF會忽略c#的實現而選擇[DbFunction()]的定義，對于本例，SQL PROFILER抓到的sql如下：
exec sp_executesql N'SELECT    ...    FROM [dbo].[TKT_Ticket_Usage] AS [Extent1]    WHERE ([Extent1].[TicketCode] = @p__linq__0) AND (((convert (datetime2, convert(varchar(255), [Extent1].[UsageDate], 102) ,  102)) = (convert (datetime2, convert(varchar(255), @p__linq__1, 102) ,  102))) OR ((convert (datetime2, convert(varchar(255), [Extent1].[UsageDate], 102) ,  102) IS NULL) AND (convert (datetime2, convert(varchar(255), @p__linq__1, 102) ,  102) IS NULL)))',N'@p__linq__0 nvarchar(4000),@p__linq__1 datetime2(7)',@p__linq__0=N'72016122817373389038',@p__linq__1='2017-02-08 00:00:00'