Why can't I use .Any()?

Question

Right off the bat I'm very new to LINQ to SQL (and C# in general) and haven't successfully implemented .Any() before. I'm using .Net 4.0 with Visual Studio 2010.

I've added a new LINQ to SQL data set to my project and I'm trying to do the following:

var db = new HealthIndicatorsDataContext();

var d = DateTime.Today;

if(db.HealthIndicators.FirstOrDefault(h => h.LogDate == d).Any())
 // do something

Unfortunately I'm receiving Cannot Resolve Sysmbol 'Any' and .Any() is highlighted in red. I've read that I needed to reference System.Core.dll in my project, I've added this but I'm still having no luck. What am I missing?

Answer 1

if(db.HealthIndicators.FirstOrDefault(h => h.LogDate == d).Any())

FirstOrDefault() returns a single item and not an IQueryable or IEnumerable - Any() is only defined on those. What you probably meant to write is:

if(db.HealthIndicators.FirstOrDefault(h => h.LogDate == d) != null))

or (better):

if(db.HealthIndicators.Any(h => h.LogDate == d)))