Declare a dictionary inside a static class

Question

How to declare a static dictionary object inside a static class  I tried  public static class ErrorCode       public const IDictionary lt string  string gt  ErrorCodeDic   new Dictionary lt string  string gt                     1    User name or password problem                    But the compiler complains that  A const field of a reference type other than string can only be initialized with null

User · Accepted Answer

If you want to declare the dictionary once and never change it then declare it as readonly:

private static readonly Dictionary<string, string> ErrorCodes
    = new Dictionary<string, string>
{
    { "1", "Error One" },
    { "2", "Error Two" }
};

If you want to dictionary items to be readonly (not just the reference but also the items in the collection) then you will have to create a readonly dictionary class that implements IDictionary.

Check out ReadOnlyCollection for reference.

BTW const can only be used when declaring scalar values inline.

User · Answer

public static class ErrorCode       public const IDictionary lt string   string  gt  m ErrorCodeDic       public static ErrorCode               m ErrorCodeDic   new Dictionary lt string  string gt                     1   User name or password problem                             Probably initialise in the constructor

User · Answer

You can use the static class constructor to initialize your dictionary   public static class ErrorCode       public const IDictionary lt string  string gt  ErrorCodeDic      public static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

public static class ErrorCode       public const IDictionary lt string   string  gt  m ErrorCodeDic       public static ErrorCode               m ErrorCodeDic   new Dictionary lt string  string gt                     1   User name or password problem                             Probably initialise in the constructor

User · Answer

Make the Dictionary a static  and never add to it outside of your static object s ctor  That seems to be a simpler solution than fiddling with the static const rules in C

User · Answer

You can use the static class constructor to initialize your dictionary   public static class ErrorCode       public const IDictionary lt string  string gt  ErrorCodeDic      public static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

The problem with your initial example was primarily due to the use of const rather than static  you can t create a non-null const reference in C    I believe this would also have worked   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic           new Dictionary lt string  string gt                    1    User name or password problem          Also  as Y Low points out  adding readonly is a good idea as well  and none of the modifiers discussed here will prevent the dictionary itself from being modified

User · Answer

Create a static constructor to add values in the Dictionary   enum Commands       StudentDetail   public static class Quires       public static Dictionary lt Commands  String gt  quire           new Dictionary lt Commands  String gt         static Quires                 quire add Commands StudentDetail   SELECT   FROM student b

User · Answer

The correct syntax   as tested in VS 2008 SP1   is this   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic       static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

Create a static constructor to add values in the Dictionary   enum Commands       StudentDetail   public static class Quires       public static Dictionary lt Commands  String gt  quire           new Dictionary lt Commands  String gt         static Quires                 quire add Commands StudentDetail   SELECT   FROM student b

User · Answer

Old question  but I found this useful   Turns out  there s also a specialized class for a Dictionary using a string for both the key and the value   private static readonly StringDictionary SegmentSyntaxErrorCodes   new StringDictionary          1    Unrecognized segment ID            2    Unexpected segment         Edit  Per Chris s comment below  using Dictionary lt string  string gt  over StringDictionary is generally preferred but will depend on your situation   If you re dealing with an older code base  you might be limited to the StringDictionary   Also  note that the following line   myDict  foo     will return null if myDict is a StringDictionary  but an exception will be thrown in case of Dictionary lt string  string gt    See the SO post he mentioned for more information  which is the source of this edit

User · Answer

public static class ErrorCode       public const IDictionary lt string   string  gt  m ErrorCodeDic       public static ErrorCode               m ErrorCodeDic   new Dictionary lt string  string gt                     1   User name or password problem                             Probably initialise in the constructor

User · Answer

You can use the static class constructor to initialize your dictionary   public static class ErrorCode       public const IDictionary lt string  string gt  ErrorCodeDic      public static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

OK - so I m working in ASP 2 x  not my choice   but hey who s bitching     None of the initialize Dictionary examples would work   Then I came across this  http   kozmic pl archive 2008 03 13 framework-tips-viii-initializing-dictionaries-and-collections aspx     which hipped me to the fact that one can t use collections initialization in ASP 2 x

User · Answer

Make the Dictionary a static  and never add to it outside of your static object s ctor  That seems to be a simpler solution than fiddling with the static const rules in C

User · Answer

The problem with your initial example was primarily due to the use of const rather than static  you can t create a non-null const reference in C    I believe this would also have worked   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic           new Dictionary lt string  string gt                    1    User name or password problem          Also  as Y Low points out  adding readonly is a good idea as well  and none of the modifiers discussed here will prevent the dictionary itself from being modified

User · Answer

OK - so I m working in ASP 2 x  not my choice   but hey who s bitching     None of the initialize Dictionary examples would work   Then I came across this  http   kozmic pl archive 2008 03 13 framework-tips-viii-initializing-dictionaries-and-collections aspx     which hipped me to the fact that one can t use collections initialization in ASP 2 x

User · Answer

The correct syntax   as tested in VS 2008 SP1   is this   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic       static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

The problem with your initial example was primarily due to the use of const rather than static  you can t create a non-null const reference in C    I believe this would also have worked   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic           new Dictionary lt string  string gt                    1    User name or password problem          Also  as Y Low points out  adding readonly is a good idea as well  and none of the modifiers discussed here will prevent the dictionary itself from being modified

User · Answer

The problem with your initial example was primarily due to the use of const rather than static  you can t create a non-null const reference in C    I believe this would also have worked   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic           new Dictionary lt string  string gt                    1    User name or password problem          Also  as Y Low points out  adding readonly is a good idea as well  and none of the modifiers discussed here will prevent the dictionary itself from being modified

User · Answer

Make the Dictionary a static  and never add to it outside of your static object s ctor  That seems to be a simpler solution than fiddling with the static const rules in C

User · Answer

The correct syntax   as tested in VS 2008 SP1   is this   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic       static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

You can use the static class constructor to initialize your dictionary   public static class ErrorCode       public const IDictionary lt string  string gt  ErrorCodeDic      public static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

public static class ErrorCode       public const IDictionary lt string   string  gt  m ErrorCodeDic       public static ErrorCode               m ErrorCodeDic   new Dictionary lt string  string gt                     1   User name or password problem                             Probably initialise in the constructor

User · Answer

The correct syntax   as tested in VS 2008 SP1   is this   public static class ErrorCode       public static IDictionary lt string  string gt  ErrorCodeDic       static ErrorCode                 ErrorCodeDic   new Dictionary lt string  string gt                    1    User name or password problem

User · Answer

Old question  but I found this useful   Turns out  there s also a specialized class for a Dictionary using a string for both the key and the value   private static readonly StringDictionary SegmentSyntaxErrorCodes   new StringDictionary          1    Unrecognized segment ID            2    Unexpected segment         Edit  Per Chris s comment below  using Dictionary lt string  string gt  over StringDictionary is generally preferred but will depend on your situation   If you re dealing with an older code base  you might be limited to the StringDictionary   Also  note that the following line   myDict  foo     will return null if myDict is a StringDictionary  but an exception will be thrown in case of Dictionary lt string  string gt    See the SO post he mentioned for more information  which is the source of this edit

User · Answer

Make the Dictionary a static  and never add to it outside of your static object s ctor  That seems to be a simpler solution than fiddling with the static const rules in C

[c#] Declare a dictionary inside a static class

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