How to use Any() instead of foreach?

Question

I need to run a stored procedure on SQL Server, using LINQ, and throw an exception if it returns any rows. The following code works, although the foreach loop does not communicate my intent well enough:

foreach (var badData in context.BadDataForDay(today)) { throw new Exception("Bad data found"); }

I wanted to write something like IF EXISTS() in SQL, but with LINQ:

var badData = from p in context.BadDataForDay(today) select p; if (badData.Any()) { throw new Exception("Bad data found"); }

This code compiles but Any() blows up with the following message:

Specified cast is not valid

What am I missing? Is Any() the right method to use in this case?

Edit: I debugged, and the code blows up before the stored procedure is called, at the following generated line:

 return ((ISingleResult<BadDataResult>)(result.ReturnValue));

To get it to work, I did the following:

I added another stored procedure and dragged it to my context:

CREATE PROCEDURE dbo.BadDataExists @AsOfDate DATETIME AS BEGIN ; SET NOCOUNT ON ; SELECT COUNT(*) AS Cnt FROM SomeTable WHERE SOME conditions ; END ;

I used this code:

 foreach (var badDataCount in context.BadDataExists(asOfDate).Where(badDataCount => badDataCount.Cnt > 0)) {

Although it works now, I would really like to understand what I was missing.

Can you post the code for the BadDataForDay method. Incidentally - when you can get it to work you should simply be able to do if(context.BadDataForDay(today).Any()) — Andras Zoltan
– Andras Zoltan, Commented Aug 8, 2011 at 14:19
is bad data really an exception? Do you expect the data to sometimes be bad? — Mitch Wheat
– Mitch Wheat, Commented Aug 8, 2011 at 14:20
I assume your foreach code would also blow up, if context.BadDataForDay(today) would return any data... — Daniel Hilgarth
– Daniel Hilgarth, Commented Aug 8, 2011 at 14:23
@Andras: I have a stored procedure BadDataForDay, and the method with this name was generated in my context when I dragged that procedure into my pad. — Arne Lund
– Arne Lund, Commented Aug 8, 2011 at 14:24

Daniel Hilgarth · Accepted Answer · 2011-08-15 18:58:46Z

I assume your foreach code would also blow up, if context.BadDataForDay(today) would return any data...

The code that translates the objects from the database into C# objects and returns them as an enumerable inside BadDataForDay seems to be performing a cast that compiles fine but that blows up at runtime, because the object that should be casted has the wrong type.

The reason why Any and foreach only blow up when data is returned is simple: Without data, no cast will be performed.

hunter · Accepted Answer · 2011-08-08 14:19:52Z

This should work:

var badData = context.BadDataForDay(today); if (badData != null && badData.Any()) { throw new Exception("Bad data found"); }

What exception is throwing?

kleinohad · Accepted Answer · 2011-08-08 17:26:33Z

Any is used with a condition like this for example (I am not sure this is what you need):

 var res = (from c in context.Cusotmer where c => c.Orders.Any(o => o.year == 2010) select c);

in your case might be:

var badData = (from p in context.BadDataForDay where p => p.Days.Any(d => d == today) select p);

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