?在用EF4.1過程中發現了一個非常詭異的GUID為空問題，不說廢話，直接看問題吧：

測試表UserInfo（SQL SERVER 2008 R2）：

?

這里是建表SQL語句，供有興趣朋友測試：

CREATE?TABLE?[dbo].[UserInfo](
????[ID]?[int]?IDENTITY(1,1)?NOT?NULL,
????[UserID]?[uniqueidentifier]?NOT?NULL,
????[UserName]?[nvarchar](50)?NULL,
????[Email]?[varchar](50)?NOT?NULL,
????[PicID]?[uniqueidentifier]?NULL,
????PRIMARY?KEY([ID])
)
GO

?

UserInfo實體類：

using?System;
using?System.Collections.Generic;
using?System.Linq;
using?System.Text;
using?System.Runtime.Serialization;
using?System.Data.Entity;
using?System.ComponentModel.DataAnnotations;

namespace?ConsoleTest
{
????[Serializable]
????[DataContract]
????[Table("UserInfo")]
????public?class?UserInfo
????{
????????[DataMember]
????????[Key]
????????public?int?ID?{?get;?set;?}

????????[DataMember]
????????public?Guid?UserID?{?get;?set;?}

????????[DataMember]
????????public?string?UserName?{?get;?set;?}

????????[DataMember]
????????public?string?Email?{?get;?set;?}

????????[DataMember]
????????public?Guid?PicID?{?get;?set;?}
????}
}

?

EF配置代碼：

using?System;
using?System.Collections.Generic;
using?System.Linq;
using?System.Text;
using?System.Data.Entity;
using?System.Configuration;

namespace?ConsoleTest
{
????public?class?TestDBContext?:?DbContext
????{
????????public?TestDBContext()
????????????:?base("Test")
????????{
????????}

????????public?DbSet<UserInfo>?UserInfos?{?get;?set;?}
????}

}

?

測試方法：

using?System;
using?System.Collections.Generic;
using?System.Linq;
using?System.Text;
using?System.Data.SqlClient;

namespace?ConsoleTest
{
????public?class?NullTest
????{
????????public?List<UserInfo>?GetUserInfo()
????????{
????????????using?(TestDBContext?context?=?new?TestDBContext())
????????????{
????????????????List<UserInfo>?users?=?context.UserInfos
????????????????????.Where(m=>m.UserID!=null)
????????????????????.Where(n=>n.UserName!=null)
????????????????????.Where(p=>p.Email!=null)
????????????????????.Where(q=>q.PicID!=null)
????????????????????.ToList();
????????????????return?users;
????????????}
????????}

????????public?List<UserInfo>?GetUserInfoNew()
????????{
????????????using?(TestDBContext?context?=?new?TestDBContext())
????????????{
????????????????List<UserInfo>?users?=?context.UserInfos
????????????????????.Where(m?=>?m.UserID?!=?Guid.Empty)
????????????????????.Where(n?=>?n.UserName?!=?null)
????????????????????.Where(p?=>?p.Email?!=?null)
????????????????????.Where(q?=>?q.PicID?!=?new?Guid("00000000-0000-0000-0000-000000000000"))
????????????????????.ToList();
????????????????return?users;
????????????}
????????}
????}

}?

?

調用：

using?System;
using?System.Collections.Generic;
using?System.Linq;
using?System.Text;
using?System.Text.RegularExpressions;

namespace?ConsoleTest
{
????class?Program
????{
????????static?void?Main(string[]?args)
????????{
????????????NullTest?nullTest?=?new?NullTest();
????????????nullTest.GetUserInfo();
????????????nullTest.GetUserInfoNew();
????????????Console.Read();
????????}
????}

}?

?

用SQL SERVER Profiler工具檢測到的第一個方法SQL語句：

SELECT?
[Extent1].[ID]?AS?[ID],?
[Extent1].[UserID]?AS?[UserID],?
[Extent1].[UserName]?AS?[UserName],?
[Extent1].[Email]?AS?[Email],?
[Extent1].[PicID]?AS?[PicID]
FROM?[dbo].[UserInfo]?AS?[Extent1]

WHERE?([Extent1].[UserName]?IS?NOT?NULL)?AND?([Extent1].[Email]?IS?NOT?NULL)?

??

?第二個方法SQL語句：

?exec?sp_executesql?N'SELECT?

[Extent1].[ID]?AS?[ID],?
[Extent1].[UserID]?AS?[UserID],?
[Extent1].[UserName]?AS?[UserName],?
[Extent1].[Email]?AS?[Email],?
[Extent1].[PicID]?AS?[PicID]
FROM?[dbo].[UserInfo]?AS?[Extent1]
WHERE?([Extent1].[UserID]?<>?@p__linq__0)?AND?([Extent1].[UserName]?IS?NOT?NULL)?AND?([Extent1].[Email]?IS?NOT?NULL)?AND?(cast(''00000000-0000-0000-0000-000000000000''?as?uniqueidentifier)?<>?[Extent1].[PicID])',N'@p__linq__0?uniqueidentifier',@p__linq__0='00000000-0000-0000-0000-000000000000'

?

詭異在第一個方法生成的SQL語句中類型為GUID的兩個字段的不為空的條件沒有了，第二個方法是本人針對第一種方法不足提供的一種解決方案，不知大家有什么看法，怎么解決這一問題的，請不吝賜教！

本文轉自Artwl博客園博客，原文鏈接：http://www.cnblogs.com/artwl/，如需轉載請自行聯系原作者

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