嵌套的LINQ方法抛出`不支持...`异常

Question

这是从这里开始的后续工作 - >multiple-sorting-on-linq-nested-method。

基本上，在let memberName = ...它抛出这个异常Method 'System.String MemberName(Int32)' has no supported translation to SQL.，我没有找出解决方案。

此外，BLLCmo和BLLConnect实际使用两个不同数据库间。原来的应用程序（不是我的）使用4个独立的数据库的，所以我试图做出应有的。

---

BLLCmo.cs

public static DataTable GetAllMembers(Guid workerID) 
    { 
     var AllEnrollees = from enrollment in context.tblCMOEnrollments 
           where enrollment.CMOSocialWorkerID == workerID || enrollment.CMONurseID == workerID 
           join supportWorker in context.tblSupportWorkers on enrollment.EconomicSupportWorkerID equals supportWorker.SupportWorkerID into workerGroup 
           from worker in workerGroup.DefaultIfEmpty() 
           let memberName = BLLConnect.MemberName(enrollment.ClientID) 
           orderby enrollment.DisenrollmentDate ascending, memberName ascending 
           select new 
             { 
              enrollment.ClientID, 
              MemberName = memberName, 
              NurseName = BLLAspnetdb.NurseName(enrollment.CMONurseID), 
              SocialWorkerName =BLLAspnetdb.SocialWorkerName(enrollment.CMOSocialWorkerID), 
              enrollment.DisenrollmentDate, 
              enrollment.EnrollmentDate, 
              ESFirstName = worker.FirstName, 
              ESLastName = worker.LastName, 
              ESPhone = worker.Phone 
             }; 

     var dataTable = AllEnrollees.CopyLinqToDataTable(); 

     return dataTable; 
    } 

---

BLLConnect.cs

public static String MemberName(Int32 personID) 
    { 
     var memberName = from person in context.tblPersons 
         where person.PersonID == personID 
         select person.FirstName + " " + person.LastName; 

     return memberName.SingleOrDefault(); 
    } 

Answer 1

的问题是，LINQ to SQL的试图您的方法转换成SQL。由于MemberName是无效的SQL，因此放弃。相反，你需要拉下你从SQL需要的数据，然后打电话给你在一个单独的LINQ方法（和排序）到对象查询：

public static DataTable GetAllMembers(Guid workerID) 
{ 
    var AllEnrollees = 
     from enrollment in context.tblCMOEnrollments 
     where enrollment.CMOSocialWorkerID == workerID || enrollment.CMONurseID == workerID 
     join supportWorker in context.tblSupportWorkers on enrollment.EconomicSupportWorkerID equals supportWorker.SupportWorkerID into workerGroup 
     from worker in workerGroup.DefaultIfEmpty() 
     select new 
     { 
      enrollment.ClientID, 
      enrollment.CMONurseID, 
      enrollment.CMOSocialWorkerID, 
      enrollment.DisenrollmentDate, 
      enrollment.EnrollmentDate, 
      ESFirstName = worker.FirstName, 
      ESLastName = worker.LastName, 
      ESPhone = worker.Phone 
     }; 

    var result = 
     from enrollee in AllEnrollees.AsEnumerable() 
     let memberName = BLLConnect.MemberName(enrollee.ClientID) 
     orderby enrollee.DisenrollmentDate ascending, memberName ascending 
     select new 
     { 
      enrollee.ClientID, 
      MemberName = memberName, 
      NurseName = BLLAspnetdb.NurseName(enrollee.CMONurseID), 
      SocialWorkerName = BLLAspnetdb.SocialWorkerName(enrollee.CMOSocialWorkerID), 
      enrollee.DisenrollmentDate, 
      enrollee.EnrollmentDate, 
      enrollee.ESFirstName, 
      enrollee.ESLastName, 
      enrollee.ESPhone 
     }; 

    return result.CopyLinqToDataTable(); 
}