Using .Count() to test for emptiness works, but using .Any() makes the intent clearer, and the code more readable.
However, there are some cases where special attention should be paid:
- if the collection is an
EntityFramework or other ORM query, calling .Count() will cause executing a potentially
massive SQL query and could put a large overhead on the application database. Calling .Any() will also connect to the database, but
will generate much more efficient SQL.
- if the collection is part of a LINQ query that contains
.Select() statements that create objects, a large amount of memory could
be unnecessarily allocated. Calling .Any() will be much more efficient because it will execute fewer iterations of the enumerable.
Noncompliant code example
Private Function HasContent(Strings As IEnumerable(Of String)) As Boolean
Return Strings.Count() > 0 ' Noncompliant
End Function
Private Function HasContent2(Strings As IEnumerable(Of String)) As Boolean
Return Strings.Count() >= 1 ' Noncompliant
End Function
Private Function IsEmpty(Strings As IEnumerable(Of String)) As Boolean
Return Strings.Count() = 0 ' Noncompliant
End Function
Compliant solution
Private Function HasContent(Strings As IEnumerable(Of String)) As Boolean
Return Strings.Any
End Function
Private Function HasContent2(Strings As IEnumerable(Of String)) As Boolean
Return Strings.Any
End Function
Private Function IsEmpty(Strings As IEnumerable(Of String)) As Boolean
Return Not Strings.Any
End Function
