Create instance of unknown Enum with string value using reflection in C#

Question

I have a problem working out how exactly to create an instance of an enum when at runtime i have the System.Type of the enum and have checked that the BaseType is System.Enum, my value is an int value matching an item in the mystery Enum.

The code i have so far is just the logic described above as shown below.

        if (Type.GetType(type) != null)
        {
            if (Type.GetType(type).BaseType.ToString() == "System.Enum")
            {
                return ???;
            }
        }

When working with Enums in the past i have always know at code time which enum i am trying to parse but in this scenario im confused and have had little luck articulating my question in a google friendly way... I would usually do something like

(SomeEnumType)int

but since i dont know the EnumType at code time how can i achieve the same thing?

Solution 1

Use the ToObject method on the Enum class:

var enumValue = Enum.ToObject(type, value);

Or like the code you provided:

if (Type.GetType(type) != null)
{
    var enumType = Type.GetType(type);
    if (enumType.IsEnum)
    {
        return Enum.ToObject(enumType, value);
    }
}

Solution 2

Use (ENUMName)Enum.Parse(typeof(ENUMName), integerValue.ToString())

as a generic function (edited to correct syntax errors)...

    public static E GetEnumValue<E>(Type enumType, int value) 
                        where E : struct
    {
        if (!(enumType.IsEnum)) throw new ArgumentException("Not an Enum");
        if (typeof(E) != enumType)
            throw new ArgumentException(
                $"Type {enumType} is not an {typeof(E)}");
        return (E)Enum.Parse(enumType, value.ToString());
    }

old wrong version:

public E GetEnumValue(Type enumType, int value) where E: struct
{
  if(!(enumType.IsEnum)) throw ArgumentException("Not an Enum");
  if (!(typeof(E) is enumType)) 
       throw ArgumentException(string.format(
           "Type {0} is not an {1}", enumType, typeof(E));
  return Enum.Parse(enumType, value.ToString());
}

Comments

[Jeppe Stig Nielsen]

Instead of enumType.BaseType == typeof(Enum) it's easier (and probably equivalent) to write enumType.IsEnum.

[Jeppe Stig Nielsen]

This seems wrong in a couple of ways. (1) Your method has a where constraint, but you forget to "define" the type E and make your method generic. (2) How is one supposed to supply E when calling the method? It is not going to be inferred by the compiler. (3) Your is expression is syntactically wrong. The right-hand side of is is an object, not a type. Maybe you meant to use != instead of is? What is the purpose? (4) The return type requires you to cast the output from the non-generic Enum.Parse method.

[Jeppe Stig Nielsen]

Why did you leave the Enum.ToObject method? I liked it much more than going through a string instance like you do now.

[Charles Bretana]

Sorry, typing without compile check. Edited to fix syntax errors.