Problem with DISTINCT and Linq2SQL - asp.net-mvc

Question

I have a table like this:
idinterpretation | iddictionary | idword | meaning
1 1 1115 hello
2 1 1115 hi
3 1 1115 hi, bro
5 1 1118 good bye
6 1 1118 bye-bye
7 2 1119 yes
8 2 1119 yeah
9 2 1119 all rigth
And i try to get distinct rows (DISTINCT idword). So, at first i tried:
return dc.interpretations.Where(i => i.iddictionary == iddict).
ToList<interpretation>().Distinct(new WordsInDictionaryDistinct()).
OrderBy(w => w.word.word1).Skip(iSkip).Take(iTake);
But i have about 300.000 rows in my table and it is wrong solution.
Then, i tried:
IEnumerable<interpretation> res = (from interp in dc.interpretations
group interp by interp.idword into groupedres
select new interpretation
{
idword = groupedres.Key,
idinterpretation = groupedres.SingleOrDefault(i => i.idword == groupedres.Key).idinterpretation,
interpretation1 = groupedres.SingleOrDefault(i => i.idword == groupedres.Key).interpretation1,
iddictionary = groupedres.SingleOrDefault(i => i.idword == groupedres.Key).iddictionary
}).Skip(iSkip).Take(iTake);
and i took error: #foreach (interpretation interp in ViewBag.Interps) System.NotSupportedException: Explicit construction of entity type 'vslovare.Models.interpretation' in query is not allowed.
Is it really a way to take distinct rows and to have in finish rows like this:
idinterpretation | iddictionary | idword | meaning
1 1 1115 hello
5 1 1118 good bye
7 2 1119 yes
?
dictionaries:
dictionary table
iddictionary | dictionary_name
words:
word table
idword | word_name
interpretations:
interpretation table
idinterpretation | iddictionary | idword | meaning

Answer 1

I think your second attempt is almost there - you probably need to use a GroupBy clause to get this working within SQL.
Something like:
var query = from row in dc.interpretations
where row.iddictionary == iddict
group row by idword into grouped
select grouped.FirstOrDefault();
return query.OrderBy(w => w.word.word1).Skip(iSkip).Take(iTake);
On why your query is taking too long - in general, if your query is slow it will be because the data you are searching and returning is really large - or because it is poorly indexed at the database level. To help find out, it is analysing or profiling your query - see this article on MSDN http://msdn.microsoft.com/en-us/magazine/cc163749.aspx