using System;

​

var name = new UserName();

Console.WriteLine(name);

public readonly record struct UserName

{

    private string Value { get; }

    public UserName(string value)

    {

        if (string.IsNullOrEmpty(value))

        {

            throw new ArgumentNullException(nameof(value));

        }

        Value = value;

    }

    public override string ToString() => $"The value is: {Value}";

}

​