Entity framework LINQ to实体无法识别该方法

我正在关注MSDN。我先把它移植到EF代码

public interface IUnitOfWork
{
    IRepository<Employee> Employees { get; }
    IRepository<TimeCard> TimeCards { get; }
    void Commit();
}

这个模型很好，因为它给了我可测试性。但是，运行像上面这样的查询会抛出

LINQ to Entities does not recognize the method
 'System.Linq.IQueryable`1[DomainModel.Models.TimeCard] FindAll()' 
  method, and this method cannot be translated into a store expression.

---

我理解这个错误，但有没有办法避免它，但仍然保留存储库以供测试？

由于

IQueryable

和查询提供程序工作的性质，无法翻译select语句：有关详细信息，请参阅此线程

您可以通过将表达式划分为以下单独语句来“帮助”linq提供程序：

var ems = unitOfWork.Employees.FindAll();
var tcs = unitOfWork.TimeCards.FindAll();

var query = from e in ems
            from tc in tcs
            where tc.Employee.Id == e.Id && e.Name.StartsWith("C")
            select tc;

---

或者，您可以让FindAll（）返回

IEnumerable

而不是

IQueryable

，这样您的原始表达式就可以工作了。

谢谢，它可以工作了。但IEnumerable是贪婪的。它将所有内容都带到内存中，并在之后进行连接。

public class SqlUnitOfWork : IUnitOfWork, IDisposable
{
    private readonly HrContext context;
    private IRepository<Employee> employees;
    private IRepository<TimeCard> timeCards;
    public SqlUnitOfWork()
    {
        this.context = new HrContext();
    }
    public IRepository<Employee> Employees
    {
        get
        {
            return new SqlRepository<Employee>(context);
        }
    }
    public IRepository<TimeCard> TimeCards
    {
        get
        {
            return new SqlRepository<TimeCard>(context);
        }
    }
    public void Commit()
    {
        this.context.SaveChanges();
    }
    public void Dispose()
    {
        context.Dispose();
    }
}

var query = from e in unitOfWork.Employees.FindAll()
            from tc in unitOfWork.TimeCards.FindAll()
            where tc.Employee.Id == e.Id && e.Name.StartsWith("C")
            select tc;
var timeCards = query.ToList();

LINQ to Entities does not recognize the method
 'System.Linq.IQueryable`1[DomainModel.Models.TimeCard] FindAll()' 
  method, and this method cannot be translated into a store expression.

var ems = unitOfWork.Employees.FindAll();
var tcs = unitOfWork.TimeCards.FindAll();

var query = from e in ems
            from tc in tcs
            where tc.Employee.Id == e.Id && e.Name.StartsWith("C")
            select tc;