Inline instantiation of a constant List

Question

I try to do something like this   public const List lt String gt  METRICS   new List lt String gt                          SourceFile LOC              SourceFile MCCABE              SourceFile NOM              SourceFile NOA              SourceFile FANOUT              SourceFile FANIN              SourceFile NOPAR              SourceFile NDC              SourceFile CALLS              But unfortunately this doesn t work   FileStorer METRICS  is of type  System Collections Generic List lt string gt    A const field of a reference type other than string can only be initialized with null    How can I solve this problem

User · Answer

You are looking for a simple code  like this       List lt string gt  tagList   new List lt string gt  new                   A            B            C            D            E

User · Answer

const is for compile-time constants  You could just make it static readonly  but that would only apply to the METRICS variable itself  which should typically be Metrics instead  by  NET naming conventions   It wouldn t make the list immutable - so someone could call METRICS Add  shouldn t be here     You may want to use a ReadOnlyCollection lt T gt  to wrap it  For example   public static readonly IList lt String gt  Metrics   new ReadOnlyCollection lt string gt       new List lt String gt              SourceFile LoC  SourceFile McCabe  SourceFile NoM           SourceFile NoA  SourceFile FanOut  SourceFile FanIn            SourceFile Par  SourceFile Ndc  SourceFile Calls       ReadOnlyCollection lt T gt  just wraps a potentially-mutable collection  but as nothing else will have access to the List lt T gt  afterwards  you can regard the overall collection as immutable    The capitalization here is mostly guesswork - using fuller names would make them clearer  IMO    Whether you declare it as IList lt string gt   IEnumerable lt string gt   ReadOnlyCollection lt string gt  or something else is up to you    if you expect that it should only be treated as a sequence  then IEnumerable lt string gt  would probably be most appropriate  If the order matters and you want people to be able to access it by index  IList lt T gt  may be appropriate  If you want to make the immutability apparent  declaring it as ReadOnlyCollection lt T gt  could be handy - but inflexible

User · Answer

You ll need to use a static readonly list instead  And if you want the list to be immutable then you might want to consider using ReadOnlyCollection lt T gt  rather than List lt T gt    private static readonly ReadOnlyCollection lt string gt   metrics       new ReadOnlyCollection lt string gt  new                         SourceFile LOC              SourceFile MCCABE              SourceFile NOM              SourceFile NOA              SourceFile FANOUT              SourceFile FANIN              SourceFile NOPAR              SourceFile NDC              SourceFile CALLS              public static ReadOnlyCollection lt string gt  Metrics       get   return  metrics

[c#] Inline instantiation of a constant List

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