IQueryable<T>查询数据库问题
_LearnerRepository = new LearnerRepository(new GAS_VeristaEntities());
var learner = _LearnerRepository.GetThemAll();
_ClassInStudentRepository = new ClassInStudentRepository(new GAS_VeristaEntities());
var cisr = _ClassInStudentRepository.GetThemAll();

上面从数据库中取出两个表的所有行。

表结构类似
learner表包括列
LearnerID   LearnerName ...
101
102
103

cisr表包括列
ClassinStudentID    LearnerID   ReceipNo
1                    101           s
2                   102           a
3                   103           s

现在给出ReceipNo，获取对应的learner表的相应行。

if (!string.IsNullOrEmpty(searchString5))   //searchString5 为ReceiptNo
{
    cisr = cisr.Where(u => u.RecieptNo == searchString5);
    foreach (var id in cisr)
    {                             
        learner = learner.Where(u => u.LearnerID == id.LearnerID);
    }              
}
这样只能取出一行数据，如果查询ReceiptNo为s,怎么查出全部行


if (!string.IsNullOrEmpty(searchString5))
{
    cisr = cisr.Where(u => u.RecieptNo == searchString5);
    bool firsttime = true;
    _LearnerRepository1 = new LearnerRepository(new GAS_VeristaEntities());
    foreach (var id in cisr)
    {
        var learner1 = _LearnerRepository1.GetThemAll();
        if (firsttime)
        {
            learner = learner.Where(u => u.LearnerID == id.LearnerID);
            firsttime = false;
        }
        else
        {
            learner = learner.Union(learner1.Where(u => u.LearnerID == id.LearnerID));
        }
    }
    firsttime = true;
}
这样试过，但learner类型有变化，后续 
public PaginatedList(IQueryable<T> source, int pageIndex, int pageSize)
{
   PageIndex = pageIndex;
   PageSize = pageSize;
   TotalCount = source.Count();   -------------这里出错。{"The specified L