Question

I return a List from a Linq query, and after it I have to fill the values in it with a for cycle.
The problem is that it is too slow.

var formentries = (from f in db.bNetFormEntries
            join s in db.bNetFormStatus on f.StatusID.Value equals s.StatusID into entryStatus
            join s2 in db.bNetFormStatus on f.ExternalStatusID.Value equals s2.StatusID into entryStatus2
            where f.FormID == formID
            orderby f.FormEntryID descending
            select new FormEntry
            {
                FormEntryID = f.FormEntryID,
                FormID = f.FormID,
                IPAddress = f.IpAddress,
                UserAgent = f.UserAgent,
                CreatedBy = f.CreatedBy,
                CreatedDate = f.CreatedDate,
                UpdatedBy = f.UpdatedBy,
                UpdatedDate = f.UpdatedDate,
                StatusID = f.StatusID,
                StatusText = entryStatus.FirstOrDefault().Status,
                ExternalStatusID = f.ExternalStatusID,
                ExternalStatusText = entryStatus2.FirstOrDefault().Status
            }).ToList();

and then I use the for in this way:

for(var x=0; x<formentries.Count(); x++)
{
    var values = (from e in entryvalues
                where e.FormEntryID.Equals(formentries.ElementAt(x).FormEntryID)
                select e).ToList<FormEntryValue>();
    formentries.ElementAt(x).Values = values;
}
return formentries.ToDictionary(entry => entry.FormEntryID, entry => entry);

But it is definitely too slow.
Is there a way to make it faster?

Answer 1

For what I see, you are iterating trough formentries 2 more times without reason – when you populate the values, and when you convert to dictionary.

If entryvalues is a database driven – i.e. you get them from the database, then put the value field population in the first query.

If it’s not, then you do not need to invoke ToList() on the first query, do the loop, and then the Dictionary creation.

var formentries = from f in db.bNetFormEntries
                join s in db.bNetFormStatus on f.StatusID.Value equals s.StatusID into entryStatus
                join s2 in db.bNetFormStatus on f.ExternalStatusID.Value equals s2.StatusID into entryStatus2
                where f.FormID == formID
                orderby f.FormEntryID descending
                select new FormEntry
                {
                    FormEntryID = f.FormEntryID,
                    FormID = f.FormID,
                    IPAddress = f.IpAddress,
                    UserAgent = f.UserAgent,
                    CreatedBy = f.CreatedBy,
                    CreatedDate = f.CreatedDate,
                    UpdatedBy = f.UpdatedBy,
                    UpdatedDate = f.UpdatedDate,
                    StatusID = f.StatusID,
                    StatusText = entryStatus.FirstOrDefault().Status,
                    ExternalStatusID = f.ExternalStatusID,
                    ExternalStatusText = entryStatus2.FirstOrDefault().Status
                };

var formEntryDictionary = new Dictionary<int, FormEntry>();

foreach (formEntry in formentries)
{
    formentry.Values = GetValuesForFormEntry(formentry, entryvalues);
    formEntryDict.Add(formEntry.FormEntryID, formEntry);
}

return formEntryDictionary;

And the values preparation:

private IList<FormEntryValue> GetValuesForFormEntry(FormEntry formEntry, IEnumerable<FormEntryValue> entryValues)
{
    return (from e in entryValues
                    where e.FormEntryID.Equals(formEntry.FormEntryID)
                    select e).ToList<FormEntryValue>();
}

You can change the private method to accept only entryId instead the whole formEntry if you wish.