EF4.1中诡异的GUID为空问题

      在用EF4.1过程中发现了一个非常诡异的GUID为空问题，不说废话，直接看问题吧：

测试表UserInfo（SQL SERVER 2008 R2）：

 

这里是建表SQL语句，供有兴趣朋友测试：

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实体类：

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配置代码：

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; }

    }

}

测试方法：

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;

            }

        }

    }

} 

调用：

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工具检测到的第一个方法SQL语句：

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) 

  

 第二个方法SQL语句：

 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'

诡异在第一个方法生成的SQL语句中类型为GUID的两个字段的不为空的条件没有了，第二个方法是本人针对第一种方法不足提供的一种解决方案，不知大家有什么看法，怎么解决这一问题的，请不吝赐教！