You'd need to iterate through all the static fields of the enum (that's how they're stored in reflection) finding the Description attribute for each one... when you spot the right one, get the value of the field.
For example:
public static T GetValue<T>(string description)
{
foreach (var field in typeof(T).GetFields())
{
var descriptions = (DescriptionAttribute[])
field.GetCustomAttributes(typeof(DescriptionAttribute), false);
if (descriptions.Any(x => x.Description == description))
{
return (T) field.GetValue(null);
}
}
throw new SomeException("Description not found");
}
(This is generic just to make it reusable for different enums.)
Obviously you'd want to cache the descriptions if you're doing this even slightly frequently, e.g.:
public static class DescriptionDictionary<T> where T : struct
{
private static readonly Dictionary<string, T> Map =
new Dictionary<string, T>();
static DescriptionDictionary()
{
if (typeof(T).BaseType != typeof(Enum))
{
throw new ArgumentException("Must only use with enums");
}
// Could do this with a LINQ query, admittedly...
foreach (var field in typeof(T).GetFields
(BindingFlags.Public | BindingFlags.Static))
{
T value = (T) field.GetValue(null);
foreach (var description in (DescriptionAttribute[])
field.GetCustomAttributes(typeof(DescriptionAttribute), false))
{
// TODO: Decide what to do if a description comes up
// more than once
Map[description.Description] = value;
}
}
}
public static T GetValue(string description)
{
T ret;
if (Map.TryGetValue(description, out ret))
{
return ret;
}
throw new WhateverException("Description not found");
}
}