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POHow can i simplify this LINQ-To-Entity query, and make it dynamic
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copied!<p>I have this query for getting data through Entity Framework, which works today. Thing is, i want to create the query dynamically, i.e build it up in blocks, but i can't figure out how exactly to do it. I believe if i can somehow save one of the values that i retrieve in the beginning i can do it, but now i retrieve it twice (probably a bit slow as well? Unless the compiler fixes it before quering). Makes sense? Here is the LINQ:</p> <pre><code>from d in db.trains where d.cancelled && d.station == toStation && d.date >= fromDate.Date && d.date <= toDate.Date && (from k in db.trains where k.date == d.date && k.trainId == d.trainId && k.stationId == fromStation && k.position <= d.position select k.trainId).Contains(d.trainId) select new { trainId = d.trainId, date = d.date, arrival = d.arrival, departure = (from k in db.trains where k.date == d.date && k.trainId == d.trainId && k.stationId == fromStation && k.position <= d.position select k.departure).FirstOrDefault() } ); </code></pre> <p>So you see, in order to get the departure, i have to retrieve the same thing again. So what i'm asking is can i save the object in the first query and then retrieve it later somehow? I can't get the syntax working. </p> <p>The database looks something like this:</p> <pre><code>trainId stationId date arrival departure position 1 99 2010-10-11 10:00 10:10 1 1 98 2010-10-11 11:20 11:30 2 1 47 2010-10-11 12:30 12:40 3 2 99 2010-10-10 15:00 15:10 5 </code></pre> <p>etc</p> <p>So bascially, i need to retrieve two objects from the db, where the first one has stationId x and the other one has stationId y and both have the same date and trainId, and they have to be in the proper order, based on position (trains go both ways, but with different trainId's).</p> <p>Also, i would like to do be able to build this query dynamically, like this:</p> <pre><code>var trains = from d in db.trains select d; if (id > 0) trains = trains.Where(p => p.trainId == id); if (date != DateTime.MinValue) trains = trains.Where(p => p.date == date); var items = (from train in trains).ToList(); </code></pre> <p>I.e based on if various variables have values.</p>

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