User-specified ErrorMessage on DataTypeAttribute get overwritten by ValidationMetadataProvider

[JaySkyworker]

[EmailAddress(ErrorMessage = "Known issue: This will be overwritten by default localized message")]
public string Email { get; set; }

[EmailAddress]
public string Email2 { get; set; }

User-specified ErrorMessage on DataTypeAttribute (EmailAddress, Phone, FileExtensions, Url, and CreditCard) get overwritten by ValidationMetadataProvider.

this is due to ValidationAttribute.ErrorMessage for DataTypeAttribute, is not null, when no ErrorMessage was assigned ( Such as Email2)

[JaySkyworker]

current work around is to have a more specific resources key defined, and write your custom error messages there.
in ValidationMetadataSharedResource.resx set
LoginModel_InputModel_Email_EmailAddress to "Your custom error message"

[JaySkyworker]

An issue at dotnet/corefx is created
https://github.com/dotnet/corefx/issues/39144