如何通过将linq中的多个表组合到实体来使用orderby

Question

我的表是，

1. 工作
2. Emp.Reg.Details
3. Emp.Plans
4. Alertsdone
5. CntactsViewed

这些是表格。通常是作业表中列出的作业列表..我在所有其他表格中进行比较..

我的linq查询

public IQueryable<Job> GetJobs()
{
    return (from job in _db.Jobs
            from ep in _db.Emp.Plans
            from al in _db.Alertsdone
            from cvc in _db.CntactsViewed

            join emps in _db.Emp.Reg.Details on job.OrganizationId equals emps.EmployerId into e
            join alr in _db.Alertsdone on ep.Alerts equals alr.AlertsSent
            join cv in _db.CntactsViewedon ep.Resumes equals cv.ContactsViewed
            from emp in e.DefaultIfEmpty()

            orderby job.OrganizationId != -1 descending, job.OrganizationId != null descending
            orderby job.OrganizationId != -1 descending, emp.EmployerId == job.OrganizationId && alr.alertssent ==ep.alerts descending, job.CreatedDate descending
            select job);
}

如果我这样给它显示空白页面..我正在尝试如果上述条件不存在意味着它应该订购其他选项，如orderby job.OrganizationId != -1 descending, job.OrganizationId != null descending ..而且我也放from emp in e.DefaultIfEmpty() ...但我错过了哪里？请帮帮我......