What is best way to create .NET6 class with many non-nullable properties?

Question

I trying to create class with some number of non-nulable properties (>7).

If I do like this:

public class Meeting
{

    public Name Name { get; set; }
    public Person ResponsiblePerson { get; set; }
    public Description Description {get; set; }
    public Category Category { get; set; }
    public Type Type { get; set; }
    public DateTime StartDate { get; set; }
    public DateTime EndDate { get; set; }
    public List<Person> Attendees { get; set; }


    public Meeting()
    {
        Attendees = new List<Person>();
    }
}

I get warnings like this: "Non-nullable property '...' must contain a non-null value when exiting constructor. Consider declaring the property as nullable."

There is a list of variants I thinked of:

• Default values removes this warning, but I think, that it will just add useless values, that in the future will be needed to be changed anyway.

• If I init all properties in constructor this warning gets away, but then constructor will have >7 params which is nightmare.

• I have seen that some people use "Builder" pattern to init classes with many params. But the builder itself can't prevent 'null' values (The builder will get same warnings).

• There is easy way to remove warning, by making nullable property in .csproj file from true to false, but I don't want to just remove that warning. I want to make class itself safe from null values.

Whats clean way create that class?

Answer 1

The whole point of non-nullable is to initialize class instances in a "valid" state. If Meeting is part of a domain, having some logic inside, you can't initialize Meeting without initial values. I.e., new Meeting() doesn't make any sense. On the other hand, if Meeting is a so-called data transfer object and it may be initialized partially, if not even empty, then setters are fine, and you don't need a constructor.