What's the best practice way to convert enum to string?

Question

Hi. I have enum like this:

public enum ObectTypes
{
    TypeOne,
    TypeTwo,
    TypeThree,
    ...
    TypeTwenty
 }

then I need to convert this enum to string. Now Im doing this that way:

public string ConvertToCustomTypeName(ObjectTypes typeObj)
{
    string result = string.Empty;
    switch (typeObj)
    {
        case ObjectTypes.TypeOne: result = "This is type T123"; break;
        case ObjectTypes.TypeTwo: result = "Oh man! This is type T234"; break;
        ...
        case ObjectTypes.TypeTwenty: result = "This is type last"; break;
    }
    return result;
}

Im quite sure that there is better way do do this, Im looking for some good practice solution.

EDIT: There is no one pattern in result string.

Thanks in advance.

Answer 1

I think the easiest way is to have a function which maps between the enum value and the preferred short name and then create another function which generates the full message.

internal static string MapToName(ObjectTypes value) {
  switch (value) { 
    case ObjectTypes.TypeOne: return "T123";
    case ObjectTypes.TypeTwo: return "T234";
    ...
  }
}

public string ConvertToCustomTypeName(ObjectTypes value) {
  return String.Format("This is type {0}", MapToName(value));
}

Answer 2

I use the [Description] attribute from System.ComponentModel

Example:

public enum RoleType
{
    [Description("Allows access to public information")] Guest = 0,
    [Description("Allows access to the blog")] BlogReader = 4,
}

Then to read from it I do

public static string ReadDescription<T>(T enumMember)
{
    var type = typeof (T);

    var fi = type.GetField(enumMember.ToString());
    var attributes = (DescriptionAttribute[]) 
            fi.GetCustomAttributes(typeof (DescriptionAttribute), false);
    return attributes.Length > 0 ? 
        attributes[0].Description : 
        enumMember.ToString();
}

Then usage

ReadDescription(RoleType.Guest);

Answer 3

If you need a custom string, the best option would be to make a Dictionary< ObjectTypes, string>, and just do a dictionary lookup.

If you're fine with the default ToString() functionality, just use typeObj.ToString();

For the dictionary approach, you could do:

private static Dictionary<ObjectTypes, string> enumLookup;

static MyClass()
{
    enumLookup = new Dictionary<ObjectTypes, string>();
    enumLookup.Add(ObjectTypes.TypeOne, "This is type T123");
    enumLookup.Add(ObjectTypes.TypeTwo, "This is type T234");
    // enumLookup.Add...

}

Your method becomes:

public string ConvertToCustomTypeName(ObjectTypes typeObj)
{
     // Shouldn't need TryGetValue, unless you're expecting people to mess  with your enum values...
     return enumLookup[typeObj];
}

Answer 4

I once used a custom attribute on the enum fields that took a string parameter and then wrote a function to extract the string when given an enum value.

Answer 5

This calls for refactoring, I'd say.

Replace Type Code With Class

Answer 6

If you simply want to use the name of enum (ie TypeOne ) you can simply call ToString() on the enum itself

typeObj.ToString()

If you want a custom string based on the type you have several different options. The switch statement you have is OK but maintaining it will get messy if you have a large number of enums. Or you could setup a dictionary based using the enum type as the key and the string as the value.

public enum ObectTypes
{
   One,
   Two
}

Dictionary<ObectTypes, String> myDic = new Dictionary<ObectTypes, string>();
myDic.Add( ObectTypes.One, "Something here for One" );
myDic.Add( ObectTypes.Two, "Something here for Two" );

Answer 7

I can't quite believe this... why has nobody suggested a Resource file?

Mapping enum values to strings within compiled code is all well and good as a quick hack, but long term it is a bad practice and makes it difficult to refactor code. What if you add (or subtract) a value from the enum? If you use strings from a resource file all you have to do is add (or remove) one entry.

Answer 8

Use the suggested Resources way:

string GetName(Enum e) {
     return Properties.Resources.ResourcesManager.GetString("_enum_"+e.GetType().ToString().Replace('.','_'));
}

Error handling is a bit more..