Question

my goal is to get lots of rows from a translation table. I use an ID to get a subset of the table (say 50 rows) then I use another ID to the rows I want from this subset. Using typed datasets I do the following to get the main dataset:

funderTextsDS.tbl_funderTextsDataTable fd =  (funderTextsDS.tbl_funderTextsDataTable)(new funderTextsDSTableAdapters.tbl_funderTextsTableAdapter()).GetData(); 

Then for each value I want to get:

fd.Select('eng_code = '' + element + '' and funderID = '' + funderID + ''')[0]['funderText'].ToString(); 

Using ANTS profiler to check the code I found that this method used about 170ms over 10 page refreshes (220 calls to the fd.select…)

When I rewrote this to LINQ it took more than 2000ms to do the same work. Here is the LINQ code I used:

IrmDatabaseContext irmDB = new IrmDatabaseContext(); irmDB.tbl_funderTexts.Single(f => f.funderID == funderId && f.eng_code == element).funderText; 

Anyone have a good way of doing this with LINQ? By looking into sql server profiler i saw that the LINQ actually generated a single select for each text i retrieved. (ie LINQ= 220 selects from the db, tableadapter method = 10 selects)

Solution: After having read around the net I found that David B was on the right track, although the for loop threw me off for quite a while. Anyway, the trick as he said, is to use a list as this actually forces linq to run the query against the DB and cache it localy. http://blogs.msdn.com/wriju/archive/2007/07/17/linq-to-sql-caching-the-query-execution.aspx.

So my solution ended up like this:

List<tbl_funderText> fd = (from tf in irmDB.tbl_funderTexts                       where tf.funderID == (int)cpcrow.cpc_fundingPartnerID                       select tf).ToList(); 

Then everytime I want an element I do:

fd.Single(f => f.eng_code == element).funderText; 

Analyzing with ANTS I then found that time was reduced to 150ms (about the same as the tableAdapter. SQL query analyzer shows that the SQL is run only one time.

Answer 1

Ah, so in the TableAdapter method, you’re pulling rows into memory and then querying those in-memory rows further. That’s easy to do in LINQ.

myDataContext dc = new myDataContext(); List<FunderText> myList = myDataContext.tbl_funderTexts.ToList();  List<string> result1 = new List<string>(); foreach(var theValue in myValues) {   result1.Add(     myList.First(f => f.funderID == theValue.funderId && f.eng_code == element).funderText   ); }