RegularExpression for either valid email or username from the comma separated list

Question

It's about the login form where some clients must enter their email and only few others their name.

Currently I have the following:

[Required(ErrorMessageResourceName = "Validation_RequiredField", ErrorMessageResourceType = typeof(Resources))]
[RegularExpression(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*", ErrorMessageResourceName = "Validation_InvalidUsername", ErrorMessageResourceType = typeof(Resources))]
public string? UserName { get; set; }

Thank you!

Answer 1

This worked just fine. Thx

@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*|[a-zA-Z]{4,}"