public class ViewModel
{
    public User CurrentUser { get ... }
    
    public List<string> Users { get ... }
    
    public bool RequireLongPasswords => true;
}

public class User
{
    [Field(Name = "First Name",
        Tooltip = "Enter your first name here.",
        Icon = PackIconKind.Account)]
    [Value(Must.NotBeEmpty)]
    public string FirstName { get; set; }

    [Field(Name = "Last Name",
        Tooltip = "Enter your last name here.")]
    [Value(Must.NotBeEmpty)]
    public string LastName { get; set; }

    [Value(Must.BeLessThan, "2020-01-01",
        Message = "You said you are born in the year {Value:yyyy}. Are you really from the future?")]
    public DateTime DateOfBirth { get; set; }

    [Field(Name = "Username")]
    [Value(Must.MatchPattern, "^[a-zA-Z][a-zA-Z0-9]*$",
        Message = "{Value} is not a valid username, usernames must match pattern {Argument}.")]
    [Value(Must.NotExistIn, "{ContextBinding Users}",
        Message = "User {Value} is already taken.")]
    public string Username { get; set; }

    [Value("Length", Must.BeGreaterThan, 6,
        Message = "Your password has {Value|Length} characters, which is less than the required {Argument}.")]
    [Value("Length", Must.BeGreaterThan, 12,
        When = "{ContextBinding RequireLongPasswords}",
        Message = "The administrator decided that your password must be really long!")]
    public string Password { get; set; }

    [Value(Must.BeEqualTo, "{Binding Password}",
        Message = "The entered passwords do not match.")]
    public string PasswordConfirm { get; set; }

    [Value(Must.BeTrue, Message = "You must accept the license agreement.")]
    public bool AgreeToLicense { get; set; }
}

using System.ComponentModel;
using System.Runtime.CompilerServices;
using MaterialForms.Wpf.Annotations;

namespace MaterialForms.Demo.Models
{
    public class FoodSelection : INotifyPropertyChanged
    {
        private string firstFood = "Pizza";
        private string secondFood = "Steak";
        private string thirdFood = "Salad";
        private string yourFavoriteFood;

        [Field(DefaultValue = "Pizza")]
        [Value(Must.NotBeEmpty)]
        public string FirstFood
        {
            get => firstFood;
            set
            {
                firstFood = value;
                OnPropertyChanged();
            }
        }

        [Field(DefaultValue = "Steak")]
        [Value(Must.NotBeEmpty)]
        public string SecondFood
        {
            get => secondFood;
            set
            {
                secondFood = value;
                OnPropertyChanged();
            }
        }

        [Field(DefaultValue = "Salad")]
        [Value(Must.NotBeEmpty)]
        public string ThirdFood
        {
            get => thirdFood;
            set
            {
                thirdFood = value;
                OnPropertyChanged();
            }
        }

        [Text("You have selected {Binding YourFavoriteFood}", InsertAfter = true)]

        [SelectFrom(new[] { "{Binding FirstFood}, obviously.", "{Binding SecondFood} is best!", "I love {Binding ThirdFood}" })]
        public string YourFavoriteFood
        {
            get => yourFavoriteFood;
            set
            {
                yourFavoriteFood = value;
                OnPropertyChanged();
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;

        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

MaterialApplication.CreateApplication();

MaterialApplication.ShutDownApplication();