Associating enums with strings in C#

Question

I know the following is not possible because it has to be an int

enum GroupTypes
{
    TheGroup = "OEM",
    TheOtherGroup = "CMB"
}

From my database I get a field with incomprehensive codes (the OEM and CMB's). I would want to make this field into an enum or something else understandable. Because the target is readability the solution should be terse.
What other options do I have?

Answer 1

My first question - Do you have access to the Database itself? This should be normalized in the database, ideally, otherwise, any solution is going to be prone to error. In my experience, data fields full of "OEM" and "CMB" tend to wind up having things like "oem " and other 'crap data' mixed in over time.... If you can normalize it, you could use the key in the table containing the elements as your Enum, and you're done, with a much cleaner structure.

If that's not available, I'd make your Enum, and make a class to parse your string into the Enum for you. This would at least give you some flexibility in handling non-standard entries and much more flexibility for trapping or handling errors than doing any of the workarounds using Enum.Parse/Reflection/etc. A dictionary would work, but could break down if you ever have case issues, etc.

I'd recommend writing a class so you can do:

// I renamed this to GroupType, since it sounds like each element has a single type...
GroupType theType = GroupTypeParser.GetGroupType(theDBString);

This preserves most of your readability without having to change the DB.

Answer 2

Why not just use ToString() on the Enum types?

private enum LogType { Error, Warning, Info};

private WriteLog(string message, LogType logType)
{
    Log.Write(message, logType.ToString());
}

Answer 3

public class DataType
{
    private readonly string value;
    private static readonly Dictionary<string, DataType> predefinedValues;

    public static readonly DataType Json = new DataType("json");
    public static readonly DataType Xml = new DataType("xml");
    public static readonly DataType Text = new DataType("text");
    public static readonly DataType Html = new DataType("html");
    public static readonly DataType Binary = new DataType("binary");

    static DataType()
    {
        predefinedValues = new Dictionary<string, DataType>();
        predefinedValues.Add(Json.Value, Json);
        predefinedValues.Add(Xml.Value, Xml);
        predefinedValues.Add(Text.Value, Text);
        predefinedValues.Add(Html.Value, Html);
        predefinedValues.Add(Binary.Value, Binary);
    }

    private DataType(string value)
    {
        this.value = value;
    }

    public static DataType Parse(string value)
    {
        var exception = new FormatException($"Invalid value for type {nameof(DataType)}");
        if (string.IsNullOrEmpty(value))
            throw exception;

        string key = value.ToLower();
        if (!predefinedValues.ContainsKey(key))
            throw exception;

        return predefinedValues[key];
    }

    public string Value
    {
        get { return value; }
    }
}

Answer 4

I was basically looking for the Reflection answer by @ArthurC

Just to extend his answer a little bit, you can make it even better by having a generic function:

    // If you want for a specific Enum
    private static string EnumStringValue(GroupTypes e)
    {
        return EnumStringValue<GroupTypes>(e);
    }

    // Generic
    private static string EnumStringValue<T>(T enumInstance)
    {
        return Enum.GetName(typeof(T), enumInstance);
    } 

Then you can just wrap whatever you have

EnumStringValue(GroupTypes.TheGroup) // if you incorporate the top part

or

EnumStringValue<GroupTypes>(GroupTypes.TheGroup) // if you just use the generic

Answer 5

I would make it into a class an avoid an enum altogether. And then with the usage of a typehandler you could create the object when you grab it from the db.

IE:

public class Group
{
    public string Value{ get; set; }
    public Group( string value ){ Value = value; } 
    public static Group TheGroup() { return new Group("OEM"); }
    public static Group OtherGroup() { return new Group("CMB"); }

}

Answer 6

I didn't need anything robust like storing the string in attributes. I just needed to turn something like MyEnum.BillEveryWeek into "bill every week" or MyEnum.UseLegacySystem into "use legacy system"--basically split the enum by its camel-casing into individiual lower-case words.

public static string UnCamelCase(this Enum input, string delimiter = " ", bool preserveCasing = false)
{
    var characters = input.ToString().Select((x, i) =>
    {

       if (i > 0 && char.IsUpper(x))
       {
           return delimiter + x.ToString(CultureInfo.InvariantCulture);
       }
       return x.ToString(CultureInfo.InvariantCulture);

    });

    var result = preserveCasing
       ? string.Concat(characters)
       : string.Concat(characters).ToLower();

    var lastComma = result.LastIndexOf(", ", StringComparison.Ordinal);

    if (lastComma > -1)
    {
       result = result.Remove(lastComma, 2).Insert(lastComma, " and ");
    }

    return result;
}

MyEnum.UseLegacySystem.UnCamelCase() outputs "use legacy system"

If you have multiple flags set, it will turn that into plain english (comma-delimited except an "and" in place of the last comma).

var myCustomerBehaviour = MyEnum.BillEveryWeek | MyEnum.UseLegacySystem | MyEnum.ChargeTaxes;

Console.WriteLine(myCustomerBehaviour.UnCamelCase());
//outputs "bill every week, use legacy system and charge taxes"