Can I use data annotations to specify an optional object property that has required properties? - data-annotations

Question

I have a simple member registration data model with a few required properties and some optional properties. The BillToAddress property is optional.
public class MemberRegistration
{
[Required(ErrorMessage = "First Name is required.")]
public string FirstName { get; set; }
[Required(ErrorMessage = "Last Name is required.")]
public string LastName { get; set; }
[Required(ErrorMessage = "Email Address is required.")]
public string EmailAddress { get; set; }
public string PhoneNumber { get; set; }
[Required(ErrorMessage = "Password is required.")]
[MinLength(7, ErrorMessage = "Password must be at least 7 characters.")]
public string Password { get; set; }
private Address m_BillToAddress;
public Address BillToAddress
{
get
{
if (m_BillToAddress == null)
{
m_BillToAddress = new Address();
}
return m_BillToAddress;
}
}
}
If the user enters an optional bill to address, I would like the street, city, country, and postal code to be required. So I defined the Address data model, marking those properties as required.
public class Address
{
[Required(ErrorMessage = "Street Line 1 is required.")]
public string Street1 { get; set; }
public string Street2 { get; set; }
public string Street3 { get; set; }
public string Street4 { get; set; }
public string Street5 { get; set; }
[Required(ErrorMessage = "City is required.")]
public string City { get; set; }
[Required(ErrorMessage = "State or Province is required.")]
public string StateOrProvince { get; set; }
[Required(ErrorMessage = "Country is required.")]
public string Country { get; set; }
[Required(ErrorMessage = "Postal Code is required.")]
public string PostalCode { get; set; }
}
But now the model validation fails when I don't supply a bill to address. How can I annotate my models so that the bill to address is optional, but if it is supplied, then it has to include street, city, country, and postal code?

Answer 1

The problem was in MemberRegistration class. Because the BillToAddress property getter always returned a new, empty Address model, BillToAddress was never null and always correctly triggered the Address class validation. I changed BillToAddress to a simple auto-implemented property:
public Address BillToAddress { get; set; }
Now if I post a MemberRegistion without a BillToAddress, it passes validation because BillToAddress is an optional property.