Question

I wonder if there is an implementation of IDictionary interface in the standard library that has property IsFixedSize == true.

In my code, I am using a Dictionary indexed by an enum, like this:

Dictionary<EMyEnum, string> myDictionary = new Dictionary<EMyEnum, string>();

I always have values in the dictionary for all possible values of MyEnum, using a code like this:

    foreach (EMyEnum myEnum in Enum.GetValues(typeof(EMyEnum)))
    {
        m_myDictionary.Add(myEnum, "");
    }

so my dictionary actually has a fixed size. It feels kind of ‘wrong’ to be using Dictionary for it and I am wondering if there is perhaps a better type I am missing.

I was looking in System.Collections.Generic and System.Collections namespaces but could not find anything suitable.

In response to one of the questions, the enum is just a bunch of values, like this:

enum EMyEnum
{
    meValue1,
    meValue2,
    meValue3
}

EDIT:

I have accepted supermem’s answer as it is most to the point of the original question. To elaborate my original concern, an ordinary dictionary can have one of the keys/items deleted and then any code that relies on the fact that iterating over keys of the dictionary also iterates over all values of enum will be broken.

I understand that I can create a fixed size array but casting enums to ints is not that pretty, besides it would only work for contiguous enums (good enough in my case).

I think there is a good case for Dictionary that has enum values as keys and it is a pity that such a class does not ship with .Net.

Answer 1

No, there are no fixed size IDictionary implementations shipping with the CLR. (Except for the ReadOnly* sort, but not applicable to your problem.)

You can roll your own, but unless you have profiled this code and determined that the use of Dictionary presents a meaningful bottleneck (IMO, very rare), I’d say to keep it as is. You also have the benefit of readability as Dictionary is very well understood and easy to grok.