C# Get Enum from Number or String

從這裡找到一個由number/string 回傳 Enum 的 generic function

public static T StringToEnum<T>(string name)
{
  return (T)Enum.Parse(typeof(T), name);
}

public T NumToEnum<T>(int number)
{
   return (T)Enum.ToObject(typeof(T), number);
}

Example:

public enum DaysOfWeek
{
   Monday,
   Tuesday,
   Wednesday,
   Thursday,
   Friday,
   Saturday,
   Sunday
}

public enum MonthsInYear
{
   January,
   February,
   March,
   April,
   May,
   June,
   July,
   August,
   September,
   October,
   November,
   December
}

DaysOfWeek d = StringToEnum<DaysOfWeek>("Monday");
//d is now DaysOfWeek.Monday

MonthsInYear m = StringToEnum<MonthsInYear>("January");
//m is now MonthsInYear.January

如果Enum中沒有相對的value, 就會throw exception:

DaysOfWeek d = StringToEnum<DaysOfWeek>("Katillsday");
//throws an ArgumentException
//Requested value "Katillsday" was not found.

它提供了一個簡單的argument check, 這就行了:

if(Enum.IsDefined(typeof(DaysOfWeek), "Katillsday"))
    StringToEnum<DaysOfWeek>("Katillsday");

可是轉眼又看到有關performance及安全性的問題:The danger of over simplification
連MSDN上也說不要用Enum.IsDefine(), M$大哥啊, 忽悠我啊?!

既然問題對我影響好像不大......就當過關了
但還是看了相關的資料, 說不定日後再要面對這個問題(希望不要)
C# Enum.Parse() Bug
More C# 'enum' Wackiness
Common Type System—Type Safety Limitations 這個讚