Tinyint(byte),SmallInt(Int16) not compatible with Enum in EF5

Question

Using Database first design and having tinyint (or smallint) column:

[MyEnumColumn] [tinyint] NOT NULL

I mapped this column to Enum Type in EDM with

External Type: NSpace.MyEnumType
Name:MyEnumType
UnderlyingType:Byte

Where NSpace.MyEnumType is defined like this:

public enum MyEnumType 
{ One, Two, Three, All }

Only to get this error when trying to load entity from context:

Schema specified is not valid. Errors:

No corresponding object layer type could be found for the conceptual type 'EntityDataModel.MyEnumType'.

The following information may be useful in resolving the previous error:

The underlying type of CLR enumeration type does not match the underlying type of EDM enumeration type.

Same applies if I use [Smallint] and [Int16] but once I change database to [Int] and enum type to [Int32] the error is gone.

Why do I need to store enum value in 4Byte (Int) data field instead of 1Byte (Tinyint) when enums in 99.9% time don't have more than 256 items or am I missing something else?

Answer 1

Well if anyone is interested the problem is in enum's default type:

public enum MyEnumType 
{ One, Two, Three, All }

Since enum defaults to type int, [Underlying Type:{Byte}] doesn't match type of [External Type] {MyEnumType:Int} so to fix it for my original tinyint field you need to define your enum like this:

public enum MyEnumType : byte
{ One, Two, Three, All }