Code inspection: Return type can be IEnumerable<T> (private accessibility)
Category: Common Practices and Code Improvements
ID: ReturnTypeCanBeEnumerable.Local
EditorConfig: resharper_return_type_can_be_enumerable_local_highlighting=[error|warning|suggestion|hint|none]
Language: C#, VB.NET
Requires SWA: No
tip
If a method returns a more generic type, it allows for more flexibility. For example, you can change the method's implementation without the need to update usages.
Also, returning a more generic type may help in the future if you decide to change the return value to a more specific type, for example, List<T>
: if callers expect IEnumerable<T>
, they will be able to accept List<T>
, but not vice versa.
Below, JetBrains Rider suggests changing the return type of GetNumbers()
from List<String>
to IEnumerable<String>
:
Note that such a replacement is not always possible, though. If methods of the derived type are used on the returned object anywhere in the current type, JetBrains Rider will not issue this suggestion.
Suboptimal code
class EnumerableTDemo{ public static void Main() { string output = string.Join(" ", GetNumbers()); Console.WriteLine(output); } private static List<string> GetNumbers() { var Numbers = new List<string> {"1", "2", "3"}; return Numbers; }}
After the quick-fix
class EnumerableTDemo{ public static void Main() { string output = string.Join(" ", GetNumbers()); Console.WriteLine(output); } private static IEnumerable<string> GetNumbers() { var Numbers = new List<string> {"1", "2", "3"}; return Numbers; }}
In some cases, however, returning a more specific type might be better. If a method is intended to work only with a specific type like an Array
, and its implementation is unlikely to be changed in the future, you can suppress this inspection for that method.