排除查询结果中的列

Question

I have an entity called EmailLog with entries such as To, From, Subject, Body, etc. in the database.

I would like to exclude Body for efficiency/performance when querying for multiple rows. Not really sure how to accomplish that. I tried using projection (see below), but I get a runtime error saying I can't project onto the Entity type.

var results = Repository.Find<EmailLog>().Select(x => new EmailLog
            {
                Id = x.Id,
                Subject = x.Subject,
                Recipient = x.Recipient,
                Status = x.Status,
                FirstAttempted = x.FirstAttempted,
                LastAttempted = x.LastAttempted,
                Attempts = x.Attempts
            });

This is understandable. I can create a new class without Body and project onto that, but I am applying some pagination to the query and don't want to evaluate the results till after I've applied pagination options. My pagination function looks like this:

public static PagedList<T> ApplyPagingAndSorting<T>(this IEnumerable<T> list, 
IPaginationOptions paginationOptions)

It takes in an enumerable list and applies Skip() and Take() to the list and then enumerates it. So how can I make sure I pass in an IEnumerable list to my function which hasn't been enumerated yet, but the associated query doesn't select Body when finally enumerated or evaluated?

Answer 1

As mentioned in my comment, calling Select() will not enumerate your result, it is one of the Linq methods that defer execution. So if you do a projection to a class without Body, you can still pass the resulting IEnumerable to your ApplyPagingAndSorting() method.