How to pass a generic Enum as dictionary key in method parameter

Question

I'm trying to create a method that counts the number of times a given Enum occurs within some existing dictionaries for reporting purposes:

private static Dictionary<string, int> CountEnumOccurrence(Dictionary<Enum, List<string>> valueSource)
{
    var convertedDictionary = new Dictionary<string, int>();

    foreach (var entry in valueSource)
    {
        var name = Enum.GetName(entry.Key.GetType(), entry.Key);
        convertedDictionary.Add(name, entry.Value.Count);
    }

    return convertedDictionary;
}

However, if I attempt to call this method like so:

var criticalFailureCounts = CountEnumOccurrence(reportSpan.criticalFailures));

I get

"cannot convert from ' System.Collections.Generic.Dictionary<Reporter.CriticalFailureCategory,System.Collections.Generic.List<string>> ' to ' System.Collections.Generic.Dictionary<System.Enum,System.Collections.Generic.List<string>> '"

Even though Reporter.CriticalFailureCategory is an Enum. I'm obviously doing this the wrong way, but I feel like there should be some way to achieve it.

Here's the definition for Reporter.CriticalFailureCategory at present:

namespace Reporter
{
    [DataContract(Namespace = "")]
    public enum CriticalFailureCategory
    {
        [EnumMember]
        ExcessiveFailures,
        [EnumMember]
        StalledInConfiguration
    }
}

The idea is that this can be expanded indefinitely without having to rewrite the code that reports on it.

Answer 1

You need to make CountEnumOccurrence generic for this to work.

private static Dictionary<string, int> CountEnumOccurrence<TEnum>(
    Dictionary<TEnum, List<string>> valueSource)
{
    var convertedDictionary = new Dictionary<string, int>();

    foreach (var entry in valueSource)
    {
        var name = Enum.GetName(entry.Key.GetType(), entry.Key);
        convertedDictionary.Add(name, entry.Value.Count);
    }

    return convertedDictionary;
}

If you want to constrain the TEnum type to only enums you can check out this question to see how and why it has to be a partially run time check or you have to write MSIL.