Question

I have the following function (which is hosted in a WCF service, if that matters):

    public List<IceVsRepositoryFile> GetRepositoryFilesByRepositoryId(int repId)
    {
        var entity = new IceVSEntities();
        var files = from p in entity.Files where p.RepositoryId == repId select p.FileId;
        List<long> iList = files.ToList();
        var repFiles = from p in entity.RepositoryFiles where iList.Contains(p.FileId) select p;

        if (!repFiles.Any())
            return null;

        var retFiles = repFiles.ToList().Select(z => new IceVsRepositoryFile
            {
                FileId = (int)z.FileId,
                RollbackFileId = (int)z.RollbackFileId,
                UserId = (int)z.UserId,
                FileContents = z.FileContents,
                ChangeDescription = z.ChangeDescription
            }).ToList();

        return retFiles;
    }

When I run this function I am getting the following an error that says “LINQ to Entities does not recognize the method ‘Boolean Contains(Int64)’ method and this method cannot be translated into a store expression.

I understand why I am getting the error message. My question is, how can I rewrite my query to make this work as expected? My backend database, if it matters, if SqlLite 3. I am using .NET 3.5.

Answer 1

The contains you used is for List, it’s not in IEnumerable so it can’t be converted to corresponding sql query. Instead you can use Any, … like:

iList.Any(x=>x == p.FileId) (or use related property)

Also instead of doing:

List<long> iList = files.ToList();

use files.Any... in your query to prevent from too many fetching from DB. Actually use IEnumerable functions instead of List functions.