CODEWITHSUNDEEP
.netentity-frameworklinq-to-sqllazy-evaluation
James Joyce
James Joyce

Reputation: 11

IQueryable Evaluation

I'm new to EF/Linq-To-SQL. I read on SO previously that IQueryable is beneficial over IEnumerable in that it does lazy evaluation. Concerning the following simple example:

var records = db.Employees.Where(x => x.EmployeeID == "3" );

if (records.Any())
{
     var topRecord = records.First();
}

Is the IQueryable expression being evaluated twice? Once to check for any elements in the result set, and once when retrieving the first element? If so, is there a more efficient way to peform such a select?

Upvotes: 1

Views: 1232

Answers (1)

LukeH
LukeH

Reputation: 269368

Yes, in this case the query will be executed twice: firstly for Any and then for First.

You could probably use FirstOrDefault instead:

var topRecord = db.Employees.FirstOrDefault(x => x.EmployeeID == "3" );
// topRecord will be null if there's no match

if (topRecord != null)
{
  ...
}

Upvotes: 4

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