C# 单元测试中mock EntityFramework中的DbFunctions中的函数




1. 写一个挡板类来提供C#代码的实现

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. 在运行时，如果是LINQ to ENTITY，EF会忽略c#的实现而选择[DbFunction()]的定义，对于本例，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'