CODEWITHSUNDEEP
c#linqentityenumerable
Andy
Andy

Reputation: 2318

What is the effect of AsEnumerable() on a LINQ Entity?

Reading the questions here and here has given me some insight into the situation, and it seems like using the AsEnumerable is memory consuming. Is there a better way to do this LINQ and the way it is done now, is the data that comes out reliable?

Removing the AsEnumerable results in a "Local sequence cannot be used in LINQ to SQL implementations of query operators except the Contains operator."

var results = from p in pollcards.AsEnumerable()
                          join s in spoils.AsEnumerable() on new { Ocr = p.OCR, fileName = p.PrintFilename } equals new { Ocr = s.seq, fileName = s.inputFileName }
                          where p.Version == null
                          orderby s.fileOrdering, s.seq
                          select new ReportSpoilsEntity
                          {
                              seq = s.seq,
                              fileOrdering = s.fileOrdering,
                              inputFileName = s.inputFileName,
                              Ocr = p.OCR,
                              ElectorName = p.ElectorName
                          };

Upvotes: 24

Views: 23002

Answers (3)

Damith Asanka
Damith Asanka

Reputation: 964

Be careful when using AsEnumerable with Entity Framework; if your table has lots of data your query may be slow because the query will first load data and then apply where clause, ordering and projection.

Upvotes: 4

Jon Skeet
Jon Skeet

Reputation: 1503110

AsEnumerable() is effectively a cast to IEnumerable<T>, which makes member resolution find members of Enumerable instead of Queryable. It's usually used when you want to force part of a query to run as SQL (or similar), and the remainder to run using LINQ to Objects.

See my Edulinq blog post on it for more information.

Now you've actually got two calls to AsEnumerable. I can see how removing the first but not the second could cause problems, but have you tried removing both?

var results = from p in pollcards
              join s in spoils
                 on new { Ocr = p.OCR, fileName = p.PrintFilename } 
                 equals new { Ocr = s.seq, fileName = s.inputFileName }
              where p.Version == null
              orderby s.fileOrdering, s.seq
              select new ReportSpoilsEntity
              {
                  seq = s.seq,
                  fileOrdering = s.fileOrdering,
                  inputFileName = s.inputFileName,
                  Ocr = p.OCR,
                  ElectorName = p.ElectorName
              };

Upvotes: 33

KristoferA
KristoferA

Reputation: 12397

Using AsEnumerable will break off the query and do the "outside part" as linq-to-objects rather than Linq-to-SQL. Effectively, you're running a "select * from ..." for both your tables and then doing the joins, where clause filter, ordering, and projection client-side.

Upvotes: 6

Related Questions