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记得以前解决这些关系的时候，头疼的要命，也没得出个完美的办法。今天看这种“延迟加载”和“立即加载”时，发现问题解决了。

                    using (DataContext cont = new DataContext())
                    {
                        cont.Log = Console.Out;
                        DataLoadOptions dl = new DataLoadOptions();
                        dl.LoadWith<UserInformation>(p => p.SecurityQuestions);
                        dl.LoadWith<UserInformation>(p => p.UsersRoles);
                        cont.LoadOptions = dl;
                        this.dataGrid1.ItemsSource = (from c in cont.UserInformation
                                                     select c).ToList<UserInformation>();
                    }

在此代码中使用的DataLoadOptions表示立即加载，而生成的实际代码，就是我们使用的内联接及外联接，上面代码生成的实际指令如下：

SELECT [t0].[id], [t0].[loginname], [t0].[username], [t0].[password], [t0].[email_address], [t0].[locked], [t0].[locked_date], [t0].[last_login_date], [t0].[created_date], [t0].[ip_address], [t0].[security_question], [t0].[security_answer], [t0].[online], [t2].[id] AS [id2], [t2].[user_id], [t2].[role_id], (
    SELECT COUNT(*)
    FROM [dbo].[users_roles] AS [t3]
    WHERE [t3].[user_id] = [t0].[id]
    ) AS [value], [t1].[id] AS [id3], [t1].[question]
FROM [dbo].[users] AS [t0]
INNER JOIN [dbo].[security_questions] AS [t1] ON [t1].[id] = [t0].[security_question]
LEFT OUTER JOIN [dbo].[users_roles] AS [t2] ON [t2].[user_id] = [t0].[id]
ORDER BY [t0].[id], [t1].[id], [t2].[id]