https://devblogs.microsoft.com/odata/odata-101-using-the-notmapped-attribute-to-exclude-enum-properties/
OData 101: Using the [NotMapped] attribute to exclude Enum properties - OData
Aug 29, 2012 - TL;DR: OData does not currently support enum types, and WCF Data Services throws an unclear exception when using the EF provider with a model that has an enum...
odatausingattributeexcludeenum