Why use IList or List?

by

There are three questions here: what type should I use for a formal parameter? What should I use for a local variable? and what should I use for a return type?

Formal parameters:

The principle here is do not ask for more than you need. IEnumerable<T> communicates “I need to get the elements of this sequence from beginning to end”. IList<T> communicates “I need to get and set the elements of this sequence in arbitrary order”. List<T> communicates “I need to get and set the elements of this sequence in arbitrary order and I only accept lists; I do not accept arrays.”

By asking for more than you need, you (1) make the caller do unnecessary work to satisfy your unnecessary demands, and (2) communicate falsehoods to the reader. Ask only for what you’re going to use. That way if the caller has a sequence, they don’t need to call ToList on it to satisfy your demand.

Local variables:

Use whatever you want. It’s your method. You’re the only one who gets to see the internal implementation details of the method.

Return type:

Same principle as before, reversed. Offer the bare minimum that your caller requires. If the caller only requires the ability to enumerate the sequence, only give them an IEnumerable<T>.

More Related Contents:

  1. how to add new method to TextBox Class [closed]
  2. Why compiler force me to specify unsafe in c# [duplicate]
  3. How to get an image size? [closed]
  4. Type.GetType(“namespace.a.b.ClassName”) returns null
  5. Using Transactions or SaveChanges(false) and AcceptAllChanges()?
  6. How do I reflect over the members of dynamic object?
  7. Structs versus classes
  8. HTML Agility pack – parsing tables
  9. Task sequencing and re-entracy
  10. page.DataContext not inherited from parent Frame?
  11. How to get the word under the cursor in Windows?
  12. How do I get the kestrel web server to listen to non-localhost requests?
  13. Static binding doesn’t update when resource changes
  14. Does C# Support Project-Wide Default Namespace Imports Like VB.NET?
  15. What are the definitions for LPARAM and WPARAM?
  16. How am I misusing the null-coalescing operator? Is this evaluating “null” correctly?
  17. Task.Yield – real usages?
  18. Images in dropdown list
  19. ef4 cause Circular reference in web service
  20. What is the difference between casting and conversion? [duplicate]
  21. C# An established connection was aborted by the software in your host machine
  22. Merge Cells in WPF DataGrid
  23. JPG to PDF Convertor in C#
  24. csc.exe reference external .dll file
  25. Input string was not in a correct format in double.Parse
  26. FtpWebRequest Download File
  27. Using Moq to override virtual methods in the same class
  28. Does any one know of a faster method to do String.Split()?
  29. Is it possible to convert VBA to C#?
  30. How do I disable the horizontal scrollbar in a Panel

Leave a Comment