Performance comparisons betweeen enum evaluations and ints

Question

Would there be difference in speed between

if (myInt == CONST_STATE1)

and

if (myEnum == myENUM.State1)

in c#?

Answer 1

In C# Enums are in-lined to be constants by the compilier anyway, so the benefit is code legibility

Answer 2

The thing to be careful about when using Enums is not to use any of the operations that require reflection (or use them with care). For example:

1. myEnumValue.ToString().
2. Enum.Parse()
3. Enum.IsDefined()
4. Enum.GetName()
5. Enum.GetNames()

In case of constants the option of doing any operations that require reflection doesn't exist. However, in case of enums it does. So you will have to be careful with this.

I have seen profile reports where operations relating to enum validations / reflections took up to 5% of the CPU time (a scenario where enum validations were done on every call to an API method). This can be greatly reduced by writing a class that caches the results of the reflection of the enum types being used.

Having said that, I would recommend making the decision of using enum vs. constant based on what makes sense from a design point of view. This is while making sure that the team is aware of the performance implications of the operations involving reflection.