System.NotImplementedException in EntityFramework linq query?

问题

Code:

var query = await _messageGroupRepository.GetAll()
                .Include(x => x.Users)
                .Where(x => x.Users.Any(y => y.Id == 1))
                .OrderByDescending(x => x.Date)
                .Take(5)
                .ToListAsync();

Result: System.NotImplementedException

Solution?

回答1:

Welcome to StackOverflow. The NotImplementedException is typically used as a placeholder in methods which are not yet implemented (as the name suggests). It should rarely occur with production code and I don't think I have ever seen it in a mature framework or library (like LINQ).

In your case, I would guess that it is the GetAll() method on your repository which throws the exception (but you can check the stacktrace), as it is the only non-LINQ method there.

回答2:

MSDN:

The exception that is thrown when a requested method or operation is not implemented.

Solution: find a method without implementation and fix it.

来源：https://stackoverflow.com/questions/59750459/system-notimplementedexception-in-entityframework-linq-query