enums.md

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Enums	default	5

Enums

Any enums exposed to Unreal Engine via UProperty/UEnum/UFunction-parameter must have a underlying type of byte. It's a restriction set by the engine with enums used in Blueprint.

If you don't need to expose them, you can have any valid underlying type.

[UEnum]
public enum EMyEnum : byte
{
    Value1 = 0,
    Value2 = 1,
}