Problem with putting a db selection result into a list? RSS

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  claudia888

  Member

  181 Points

  435 Posts

  Problem with putting a db selection result into a list?

  Apr 29, 2012 11:09 PM|LINK

  Hi,

  I'm building a MVC3 app, and encountered a problem - I searched all over and saw other people having the same problem (with the same error message), but have not seen a good solution suggested.

  What I'm trying to do is: put a db selection result into a list, or array. Here is my code:

  1st Try:

  IList<string> myList = (from c in db.Table1
                                        where .....
                                        orderby c.CID
                                        select c.MyColumn).ToList();

  2nd Try:

  var rows= from c in db.Table1

                  where .....
                  orderby c.CID
                  select c.MyColumn;

  List<string> myList = rows.ToList();

  3rd Try: // trying to put the result in an Array

  var rows= from c in db.Table1

                  where .....
                  orderby c.CID
                  select c.MyColumn;

  string[] myArray = new string[4];   // I know the length will be 4
  myArray = rows.ToArray();

  ALL the above 3 implementations gave me the same error message in VS:

  NotSupportedException was unhandled by user code.

  The LINQ expression node type 'ArrayIndex' is not supported in LINQ to Entities.

  Can anyone help or give a hint? Is there a workround? I've been stuck here for almost 2 days...really appreciate any advice!

  Thanks!

  CLaudia

• • Reply
  

  Dan Bracuk

  Contributor

  3970 Points

  1096 Posts

  Re: Problem with putting a db selection result into a list?

  Apr 29, 2012 11:12 PM|LINK

  If your query returned it's results to a DataTable, you could always loop through the rows with a foreach construct.

• • Reply
  

  jsiahaan

  Contributor

  2314 Points

  588 Posts

  Re: Problem with putting a db selection result into a list?

  Apr 29, 2012 11:50 PM|LINK

  Hi,

  Try this:

  var rows = (from a in context.ProductCategories
                            select a.Name).ToList();
  
              List<string> myList = rows as List<string>;

  Hope can help

  Jannen Siahaan
  Indonesian Humanitarian Foundation
  • Edited by jsiahaan on Apr 30, 2012 12:00 AM
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  jsiahaan

  Contributor

  2314 Points

  588 Posts

  Re: Problem with putting a db selection result into a list?

  Apr 30, 2012 12:02 AM|LINK

  Hi,

  For better performance you may write like this:

  List<string> myList = (from a in context.ProductCategories
                                     select a.Name).ToList() as List<string>;

  I have test them both with my prevoius reply.

  Have fun.

  Jannen Siahaan
  Indonesian Humanitarian Foundation
• • Reply
  

  claudia888

  Member

  181 Points

  435 Posts

  Re: Problem with putting a db selection result into a list?

  Apr 30, 2012 02:55 AM|LINK

  HI Jannen,

  Thanks for the suggestions. I tried your code - Unfortunately I still get the exactly same error message.

  Thanks,

  Claudia

• • Reply
  

  claudia888

  Member

  181 Points

  435 Posts

  Re: Problem with putting a db selection result into a list?

  Apr 30, 2012 03:02 AM|LINK

  Hi Dan,

  Thanks for trying to help. I actually tried that ... by using a froeach loop like this:

  foreach (var item in rows)

  But I got the exactly same error message for this line as well, for the "foreach" part - indicated by IntelliSense.

  Any thoughts?

  Thanks,

  Claudia

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  jsiahaan

  Contributor

  2314 Points

  588 Posts

  Re: Problem with putting a db selection result into a list?

  Apr 30, 2012 03:32 AM|LINK

  Hi Claudia,

  It's so strange, I tested the code I have replied to you and It works fine.

  Can you give the class of db.Table1?

  There should be an error somewhere.

  Have fun

  Jannen Siahaan
  Indonesian Humanitarian Foundation
  • Edited by jsiahaan on Apr 30, 2012 03:37 AM
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  jsiahaan

  Contributor

  2314 Points

  588 Posts

  Re: Problem with putting a db selection result into a list?

  May 07, 2012 09:35 AM|LINK

  Hi

  Has the problem solved?

  Regards

  Jannen Siahaan
  Indonesian Humanitarian Foundation
• • Reply
  

  claudia888

  Member

  181 Points

  435 Posts

  Re: Problem with putting a db selection result into a list?

  May 10, 2012 12:36 AM|LINK

  Hi Jsiahaan,

  I did not find out why I cannot put a db selection result directly into an array or list.

  I did get around the problem by using:

  ViewBag.MyList = rows.ToList();

  Not sure why this works, but my original code does not. Either way, I continue to move forward now.

  Thanks,

  Claudia