With Entity Framework is it better to use .First() or .Take(1) for "TOP 1"?
entity-framework, ienumerable, linq, linq-to-objects, sql
Solution
From LINQPad:
C#:
age_Centers.Select(c => c.Id).First();
age_Centers.Select(c => c.Id).FirstOrDefault();
age_Centers.Select(c => c.Id).Take(1).Dump();
SQL:
SELECT TOP (1) [t0].[Id]
FROM [age_Centers] AS [t0]
GO
SELECT TOP (1) [t0].[Id]
FROM [age_Centers] AS [t0]
GO
SELECT TOP (1) [t0].[Id]
FROM [age_Centers] AS [t0]
*Note that `Take(1)` enumerates and returns an `IQueryable`.
Problem
We are implementing some EF data repositories, and we have some queries which would include `TOP 1` I have read many posts suggesting to use `.Take(1)` The code I'm reviewing uses `.First()` I understand that both of these produce the same result for the object assignment, but do they both actually resolve to the same query? When the DB is queried, will it actually be with `TOP 1` for both requests? Or will they execute the query in full into the enumerable, then simply take the first entry in the collection? Furthermore, if we used `.FirstOrDefault()` then why should we expect any different behavior? I know that when using an IEnumerable, calling `.First()` on an empty collection will throw, but if this is actually only changing the query to include `TOP 1` then I should expect absolutely no functional difference between `.First()` and `.FirstOrDefault()`.... right? Alternatively, is there some better method than these Enumerable extentions for making the query execute `TOP 1`?