请问EF中对可为null的日期字段进行判断时如何转换？

romanchaos 2014-06-24 06:03:17

linq to sql直接convert.todatetime就行了，ef用date.value不行，用System.Data.Objects.EntityFunctions.DiffDays和System.Data.Objects.SqlClient.SqlFunctions.DateDiff都直接报：

LINQ to Entities 不识别方法“System.Nullable`1[System.Int32] DiffDays(System.Nullable`1[System.DateTime], System.Nullable`1[System.DateTime])”，因此该方法无法转换为存储表达式。

LINQ to Entities 不识别方法“System.Nullable`1[System.Int32] DateDiff(System.String, System.Nullable`1[System.DateTime], System.Nullable`1[System.DateTime])”，因此该方法无法转换为存储表达式。

请问该用什么方法？以下是linq语句：



var str = from p in db.UnsalableSalesRptReasons

                               where !p.UnsalableRpt.IsFiling

                               && p.CeateTime != null

                               //&& System.Data.Objects.EntityFunctions.DiffDays(p.CeateTime, DateTime.Now) > 30

                               && System.Data.Objects.SqlClient.SqlFunctions.DateDiff("D", p.CeateTime, DateTime.Now) > 1

                               select p.UnsalableRpt.ItemId;

其中p.CeateTime是datetime?类型

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romanchaos 2014-06-26

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引用 7 楼 save4me 的回复:

参考: LINQ + EntityFunctions in asp.net mvc
引用
However, Entity Framework 6 has removed the dependency on System.Data.Entity and has redefined all necessary classes for that purpose inside of the EntityFramework assembly. Meaning that, in the case of your console app, I am guessing that either by design (System.Data.Entity is not referenced) or by accident (System.Data.Entity is referenced but the EntityFunctions class is taken from EntityFramework.dll), the correct version of EntityFunctions (from EntityFramework.dll) is taken. If you are using any version of Entity Framework 6, make sure that you are using the EntityFunctions class that can be found in EntityFramework.dll, not the one in System.Data.Entity. Source code of EntityFunctions.cs in Entity Framework 6 Actually, if you use Entity Framework 6, I would recommend removing all and any references to System.Data.Entity - in order to avoid any future confusion and mistake.
因为Entity Framework 6把System.Data.Entity的依赖关系已经移除了，放到了EntityFramework.dll，他建议在Entity Framework 6把所有的System.Data.Entity的引用删除，避免歧义和错误。你也试一下。 [quote=引用 5 楼 romanchaos 的回复:] [quote=引用 4 楼 dongxinxi 的回复:] 在前面加个条件 && p.CreatedDate.HasValue (对应SQL语句的 is not null) && SqlFunctions.DateDiff("D", p.CreatedDate, DateTime.Now)

不行，他还是报无法转换为存储表达式的异常，其实问题应该是出在ef生成sql语句的过程中，它不会管前面是否有HasValue的，而是将HasValue和DateDiff都转成sql语句，但我网上搜来搜去别人都是直接用EntityFunctions.DiffDays或者SqlFunctions.DateDiff就可以的，但在我这就报错。另外我用的是EF6.0会不会有版本问题？或者说还要引入一些什么dll？[/quote][/quote] thx~明天试试~

romanchaos 2014-06-26

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引用 6 楼 sp1234 的回复:

使用sql语句进行查询吧。你不会学了EF，就把直接的ado.net给忘记了吧。

没办法……团队还停留在sql语句散布在三层的级别，这是我做的一个同步器顺用于踩坑，打算重构时集体转EF……

save4me 2014-06-26

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谢谢分享问题的解决方法

引用 10 楼 romanchaos 的回复:

[quote=引用 7 楼 save4me 的回复:] 参考: LINQ + EntityFunctions in asp.net mvc
引用
However, Entity Framework 6 has removed the dependency on System.Data.Entity and has redefined all necessary classes for that purpose inside of the EntityFramework assembly. Meaning that, in the case of your console app, I am guessing that either by design (System.Data.Entity is not referenced) or by accident (System.Data.Entity is referenced but the EntityFunctions class is taken from EntityFramework.dll), the correct version of EntityFunctions (from EntityFramework.dll) is taken. If you are using any version of Entity Framework 6, make sure that you are using the EntityFunctions class that can be found in EntityFramework.dll, not the one in System.Data.Entity. Source code of EntityFunctions.cs in Entity Framework 6 Actually, if you use Entity Framework 6, I would recommend removing all and any references to System.Data.Entity - in order to avoid any future confusion and mistake.
因为Entity Framework 6把System.Data.Entity的依赖关系已经移除了，放到了EntityFramework.dll，他建议在Entity Framework 6把所有的System.Data.Entity的引用删除，避免歧义和错误。你也试一下。 [quote=引用 5 楼 romanchaos 的回复:] [quote=引用 4 楼 dongxinxi 的回复:] 在前面加个条件 && p.CreatedDate.HasValue (对应SQL语句的 is not null) && SqlFunctions.DateDiff("D", p.CreatedDate, DateTime.Now)

romanchaos 2014-06-26

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引用 7 楼 save4me 的回复:

参考: LINQ + EntityFunctions in asp.net mvc
引用
However, Entity Framework 6 has removed the dependency on System.Data.Entity and has redefined all necessary classes for that purpose inside of the EntityFramework assembly. Meaning that, in the case of your console app, I am guessing that either by design (System.Data.Entity is not referenced) or by accident (System.Data.Entity is referenced but the EntityFunctions class is taken from EntityFramework.dll), the correct version of EntityFunctions (from EntityFramework.dll) is taken. If you are using any version of Entity Framework 6, make sure that you are using the EntityFunctions class that can be found in EntityFramework.dll, not the one in System.Data.Entity. Source code of EntityFunctions.cs in Entity Framework 6 Actually, if you use Entity Framework 6, I would recommend removing all and any references to System.Data.Entity - in order to avoid any future confusion and mistake.
因为Entity Framework 6把System.Data.Entity的依赖关系已经移除了，放到了EntityFramework.dll，他建议在Entity Framework 6把所有的System.Data.Entity的引用删除，避免歧义和错误。你也试一下。 [quote=引用 5 楼 romanchaos 的回复:] [quote=引用 4 楼 dongxinxi 的回复:] 在前面加个条件 && p.CreatedDate.HasValue (对应SQL语句的 is not null) && SqlFunctions.DateDiff("D", p.CreatedDate, DateTime.Now)

exception92 2014-06-25

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date.value.Day??

save4me 2014-06-25

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参考: LINQ + EntityFunctions in asp.net mvc

引用

However, Entity Framework 6 has removed the dependency on System.Data.Entity and has redefined all necessary classes for that purpose inside of the EntityFramework assembly. Meaning that, in the case of your console app, I am guessing that either by design (System.Data.Entity is not referenced) or by accident (System.Data.Entity is referenced but the EntityFunctions class is taken from EntityFramework.dll), the correct version of EntityFunctions (from EntityFramework.dll) is taken. If you are using any version of Entity Framework 6, make sure that you are using the EntityFunctions class that can be found in EntityFramework.dll, not the one in System.Data.Entity. Source code of EntityFunctions.cs in Entity Framework 6 Actually, if you use Entity Framework 6, I would recommend removing all and any references to System.Data.Entity - in order to avoid any future confusion and mistake.

因为Entity Framework 6把System.Data.Entity的依赖关系已经移除了，放到了EntityFramework.dll，他建议在Entity Framework 6把所有的System.Data.Entity的引用删除，避免歧义和错误。你也试一下。

引用 5 楼 romanchaos 的回复:

[quote=引用 4 楼 dongxinxi 的回复:] 在前面加个条件 && p.CreatedDate.HasValue (对应SQL语句的 is not null) && SqlFunctions.DateDiff("D", p.CreatedDate, DateTime.Now)

以专业开发人员为伍 2014-06-25

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使用sql语句进行查询吧。你不会学了EF，就把直接的ado.net给忘记了吧。

romanchaos 2014-06-25

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引用 4 楼 dongxinxi 的回复:

在前面加个条件 && p.CreatedDate.HasValue (对应SQL语句的 is not null) && SqlFunctions.DateDiff("D", p.CreatedDate, DateTime.Now)

IE11下面经常卡到爆 2014-06-25

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在前面加个条件 && p.CreatedDate.HasValue (对应SQL语句的 is not null) && SqlFunctions.DateDiff("D", p.CreatedDate, DateTime.Now)

save4me 2014-06-25

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参考: EntityFunctions 类在Linq可以使用


//Value1 和 dateValue2 之间的月数。
DiffMonths(p.CreatedDate, DateTime.Now)
//dateValue1 和 dateValue2 之间的天数。
DiffDays(p.CreatedDate, DateTime.Now)

或者System.Data.Entity.SqlServer.SqlFunctions. Entity Framework 6 SqlFunctions DateDiff not implemented in nuget package


p =>  SqlFunctions.DateDiff("D", p.CreatedDate, DateTime.Now)

romanchaos 2014-06-25

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引用 1 楼 duanzi_peng 的回复:

date.value.Day??

不，作为条件我要搜一个月之前的数据

譬如： public int? FlowStatus { get; set; } public DateTime? UpdateTime { get; set; } 　　

传入一个实体 student(){id = 1,name = "测试" age = null,sex = null} 下面是修改的方法 public async Task EditAsync(T model, bool IsSava = true) { _Db.Configuration.ValidateOnSaveEnabled =...

使用lambda获取某个字段的值时，数据为null的情况会直接报错，在最后加上?.value 和?? 就可以解决了

原文:EF部分字段更新，自动忽略null字段某个项目里的update代码是类似这样的 public T Update<T>(T entity) where T : ModelBase { var set = this.Set<T>(); set.Attach(entity); ...

update table_name where id = ? 这个显然是对象所有字段都为null才会出现的错误语句，如果是只有几个字段为null，在代码中增加判空还算快捷但如果出现需要判断的字段过多的情况，仍采取将每一个属性判断null的方法就显得比较麻烦和不太聪明的样子（????）那么，利用反射机制实现对象属性全部为null的判断就显得极为方便了 import java.lang.reflect.Field; public class CheckObjectNullUtil {

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