C#•14h ago

How to prevent nulls using this approach for Object Initializers?

In C# I have this class:

using System.Diagnostics.CodeAnalysis;
using System.Net.Mail;

namespace Domain.Customers;

public class EmailAddress
{
    private MailAddress email;

    public EmailAddress()
    {
        // Default constructor so I can use object initializer.
    }

    [SetsRequiredMembers]
    public EmailAddress(string email)
    {
        Email = email;
    }
    public required string Email
    {
        get => email.ToString();
        set => email = new MailAddress(value);
    }

}

using System.Diagnostics.CodeAnalysis;
using System.Net.Mail;

namespace Domain.Customers;

public class EmailAddress
{
    private MailAddress email;

    public EmailAddress()
    {
        // Default constructor so I can use object initializer.
    }

    [SetsRequiredMembers]
    public EmailAddress(string email)
    {
        Email = email;
    }
    public required string Email
    {
        get => email.ToString();
        set => email = new MailAddress(value);
    }

}

As you can see I have two constructors, when using object initializers I need to use one of them. I like using object initializers using no constructor aka the default constructor but because I added it there is no default so I added it. But now the problem is that people can call new EmailAddress() without passing an email and it can stay null that way? How can I still be able to have an empty constructor so I can use object initializers without having the risk somoene calls new EmailAdress();?

9 Replies

Angius•14h ago

The property is required, so it should enforce it being set during initialization

MODiX•14h ago

Angius

REPL Result: Failure

public class EmailAddress
{
    private MailAddress email;

    public EmailAddress()
    {
        // Default constructor so I can use object initializer.
    }

    [SetsRequiredMembers]
    public EmailAddress(string email)
    {
        Email = email;
    }
    public required string Email
    {
        get => email.ToString();
        set => email = new MailAddress(value);
    }
}

var e = new EmailAddress();

public class EmailAddress
{
    private MailAddress email;

    public EmailAddress()
    {
        // Default constructor so I can use object initializer.
    }

    [SetsRequiredMembers]
    public EmailAddress(string email)
    {
        Email = email;
    }
    public required string Email
    {
        get => email.ToString();
        set => email = new MailAddress(value);
    }
}

var e = new EmailAddress();

Exception: CompilationErrorException

- Required member 'EmailAddress.Email' must be set in the object initializer or attribute constructor.
- The type or namespace name 'MailAddress' could not be found (are you missing a using directive or an assembly reference?)
- The type or namespace name 'SetsRequiredMembersAttribute' could not be found (are you missing a using directive or an assembly reference?)
- The type or namespace name 'SetsRequiredMembers' could not be found (are you missing a using directive or an assembly reference?)
- The type or namespace name 'MailAddress' could not be found (are you missing a using directive or an assembly reference?)

- Required member 'EmailAddress.Email' must be set in the object initializer or attribute constructor.
- The type or namespace name 'MailAddress' could not be found (are you missing a using directive or an assembly reference?)
- The type or namespace name 'SetsRequiredMembersAttribute' could not be found (are you missing a using directive or an assembly reference?)
- The type or namespace name 'SetsRequiredMembers' could not be found (are you missing a using directive or an assembly reference?)
- The type or namespace name 'MailAddress' could not be found (are you missing a using directive or an assembly reference?)

Compile: 459.912ms | Execution: 0.000ms | React with ❌ to remove this embed.

Angius•14h ago

As you can see, a compile error

Jiry_XD•13h ago

Oh so they can't call the empty constructor witouth a initializer that sets the email? Thanks 🙂 Coming from java its a bit getting used to the initializers and auto setters and getters but I am getting the hang of it 😛 Another related question, in EF Core I can do:

 [EmailAddress]
 [NotMapped]
 public EmailAddress? EmailAddress { get; set; }

 [EmailAddress]
 [NotMapped]
 public EmailAddress? EmailAddress { get; set; }

This is in Customer.cs entity. I guess EmailAddress is then not getting stored to the db because it is not mapped. I don't need it mapped I just need to store it as a string. What would be a clean way to do this?

Angius•13h ago

EF entities should only contain what the table is supposed to contain

Jiry_XD•13h ago

Right, so I want to get the value out of EmailAddress string and store that. (I read about primitive obsession, ... that is why I am trying it this way)

Angius•13h ago

Use a converter, or something like Vogen that comes with such converters

Jiry_XD•13h ago

Hmm I'll look into that, thanks

333fred•12h ago

Is there a particular reason you're including both of those constructors? It seems a bit weird

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How to prevent nulls using this approach for Object Initializers?