Function to Load Enum-Typed Properties from Database

8 Comments

• To further constrain the input for T, add a type constraint of where T: struct. You can't use : enum, so struct is the next best thing.
  
  Another handy utility enum function I use quite often:
  
  public static T ParseEnum(string value) where T: struct
  {
  return (T)Enum.Parse(typeof(T), value, true);
  }
  

• I've been looking at the implementation of Enum.ToObject(Type, int) (using Lut'z Reflector, of course), but can't seem to think of a reason to use it. Why not cast the int directly to it's enum?
  
  MyEnum = (MyEnum)typeValue;
  

• Can you demo the usage?
  

• As for the usage, consider an enum named MyEnum and a variable of that enum type that you want to load from an int value, possibly one you've stored in the database -- just do the following:
  
  MyEnum test = ToEnum(value);
  
  As for the direct cast, that's a good question, and I could have sworn I'd tried that many times and it didn't work -- although it did just now in my test. Maybe I'm thinking of a limitation I encountered in .net v1 that I've been working around -- but maybe I'm wrong there as I didn't retest that assumption. Oh well, it seems that its not necessary for .net v2 at any rate, and if you have generics then you have .net v2, so mute point I suppose.
  
  Thanks for the comments.
  

• I would throw something like this into your helper:
  
  System.Diagnostics.Debug.Assert(typeof(T).IsEnum);
  

• all these helper function can not ensure valid value of enum.
  
  at .net 2.0,
  
  MyEnum test = ToEnum(value);
  
  support MyEnum only have two enum value, and the value is 10, no exception will throw. So i don't know MyEnum test now have a invalid value.
  

• You can call Enum.IsDefined in the helper function first to guarantee a valid value, and if it fails then throw an exception. The same problem occurs with the simple cast syntax, so at least using a helper function makes it easier to add extra things like this when you find it is needed.
  

• Be careful about the performance of enum operations.