I’m learning model binding and validation for C# .NET 8 Razor Pages. I set up a simple input model to test validation (from ASP.NET Core Razor Pages in Action, Mike Brind):

        public class InputModel
        {
            [Required]
            public string CountryName { get; set; }
            [Required, StringLength(2, MinimumLength = 2)]
            public string CountryCode { get; set; }
        }

However I get the following compiler warning:

Warning CS8618 Non-nullable property 'CountryName' must contain a non-null value when exiting constructor. Consider declaring the property as nullable., same for CountryCode.

It’s easy enough to understand I should assign a value to CountryName and CountryCode, or set them to nullable, but what is most correct and why?

1. public string CountryName { get; set; } = default!;
2. public string CountryName { get; set; } = string.Empty;
3. public string CountryName { get; set; } = "";
4. public string? CountryName { get; set; }
5. public string? CountryName { get; set; } = default;
6. Something else