Question

Problem

I use linq to return a list of anonymous objects

from s in _subsidiaryService.Repository.Query()
   where  s.Title.ToLower().Contains(term) ||
   s.Description.ToLower().Contains(term) ||
   s.District.ToLower().Contains(term)
   select new
              {
                  label = s.Title
                  ,
                  desc = s.Description
                  ,
                  value = s.ID
                  ,
                  icon = Url.Content(Path.Combine(string.Format(Constants.RelativePathSubsidiary, s.ID), SmallIconFileName))  //Problem line!!
              }

The line icon is where the problem is

Linq to Entities does not recognize Path.Combine or string.Format

Questions

I have two questions:

1. How can I run and Path.Combine string.format inside my queries
2. How do I create functions that run inside my queries? e.g:

Code sample

from s in _subsidiaryService.Repository.Query()
   where  s.Title.ToLower().Contains(term) ||
   s.Description.ToLower().Contains(term) ||
   s.District.ToLower().Contains(term)
   select new
              {
                  label = s.Title
                  ,
                  desc = s.Description
                  ,
                  value = s.ID
                  ,
                  icon = getIconPath(s.SmallIconFileName)
              }

My method

public string getIconPath(Guid id, sring fileName) {
    return Url.Content(Path.Combine(string.Format(Constants.RelativePathSubsidiary, id), fileName));
}

Answer 1

Change it to:

(from s in _subsidiaryService.Repository.Query()
where  s.Title.ToLower().Contains(term) ||
s.Description.ToLower().Contains(term) ||
s.District.ToLower().Contains(term)
select s).AsEnumerable().Select(s => new { label = s.Title, desc = s.Description, value = s.ID, icon = getIconPath(s.SmallIconFileName) });

The .AsEnumerable() switches it from the query to in memory operations, so it doesn’t try to map the functions to the database.

Its worth noting though that this means it runs everything up to the .AsEnumerable on the database, pulls it locally to an IEnumerable then starts iterating it to do the anonymous object creation. So there are performance implications to doing this. It may be worthwhile to trim the columns you are selecting by using an anonymous object or making sure all of your Where filtering is done prior to the AsEnumerable.