Question

How can I effective extend enum to have more than 2 options.
I am reading events from a file, line-by-line.
I have a constructor

public enum EventType
{ A,D }

public class Event
{
    public EventType Type { get; set; }

}

I assigned Type property like this:

 Type = tokens[2].Equals("A") ? EventType.A : EventType.D,

where token[2] is the string that holds values like “A”.

This works fine when there are only A and D, but I want to have 2 more types; say R and C. When I add them to enum field, how can I get the type? The above is giving compilation errors as if using Type as a variable.

I appreciate your immediate help!
Thanks

Answer 1

There are really only three sensible ways to go about this:

Enum.TryParse

If the tokens will always correspond exactly to your enum members, you can use Enum.TryParse:

EventType type;
if (Enum.TryParse(tokens[2], out type)) {
    Type = type;
}
else { /* token does not exist as an enum member */ }

This approach is the simplest, but it’s probably slower than the next one and it also has another drawback: the author of the code that provides tokens[2] and the author of the enum must always keep their code in sync.

Use a dictionary

var dict = new Dictionary<string, EventType>
{
    { "A", EventType.A },
    { "D", EventType.D },
    // more items here
}

Type = dict[tokens[2]]; // no error checking, please add some

This requires some setup, but it’s probably the fastest and it also allows accounting for changes in the input strings and/or enum values.

Use an attribute

Alternatively, you can annotate your enum members with a custom attribute and write a helper method that uses reflection to find the correct member based on the value of this attribute. This solution has its uses but it’s the least likely candidate; most of the time you should prefer one of the two alternatives.