如何将 List 转换为隐式运算符类型

Question

我正在尝试学习 MVVM，并在我的 ViewModel 中添加了将模型转换为 ViewModel 的隐式运算符，反之亦然，但现在的问题是如何将模型列表转换为 ViewModel 列表？

以下是我尝试用于列表转换但不起作用的结构代码：

Person.cs

class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

PersonViewModel.cs

 class PersonViewModel : Person
{
    public string FullName { get; set; }

    public static implicit operator List<PersonViewModel>(IList<Person> person)
    {
        if (person == null)
            return null;

        return person.Select(c => new PersonViewModel(c)).ToList(); // This is not working

    }

    public static implicit operator PersonViewModel(Person person)
    {
        return new PersonViewModel
        {
            FirstName = person.FirstName,
            LastName = person.LastName,
        };
    }

    public static implicit operator Person(PersonViewModel personViewModel)
    {
        return new Person
        {
            FirstName = personViewModel.FirstName,
            LastName = personViewModel.LastName,
        };
    }

}

Answer 1

尝试使用 Cast

person.Cast<PersonViewModel>().ToList();

更新

这会给您带来其他错误。您可以使用扩展方法并在需要时显式调用它们。像这样的东西（确保你最终检查空值）

    class Person
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }

    class PersonViewModel : Person
    {
        public string FullName { get; set; }
    }

    static class ConversionHelpers
    {
        public static Person ToPerson(this PersonViewModel pvm)
        {
            return new Person()
            {
                FirstName = pvm.FirstName,
                LastName = pvm.LastName
            };
        }

        public static PersonViewModel ToPersonViewModel(this Person p)
        {
            return new PersonViewModel()
            {
                FirstName = p.FirstName,
                LastName = p.LastName
            };
        }

        public static IEnumerable<PersonViewModel> ToPersonViewModels(IEnumerable<Person> persons)
        {
            return persons.Select(p => p.ToPersonViewModel());
        }
    }

Answer 2

很抱歉，您的“MVVM 模式”对我来说似乎有点奇怪。
这是我对MVVM模式的理解

//Model
class Person
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

//ModelWrapper which implements INotifyPropertyChanged if Model doesn't
//Here you can add additional properties which will serve a View's needs
class PersonModelWrapper
{
    private Person _Model;

    //Through this constructor you will create instance of modelwrapper
    //without any conversions
    public PersonModelWrapper (Person model)
    {
        _Model = model;
    }

    public string FirstName 
    { 
        get 
        { 
            return _Model.FirstName; 
        }
        set 
        {
            _Model.FirstName = value; 
        }
    }
    public string LastName
    { 
        get 
        { 
            return _Model.LastName; 
        }
        set 
        {
            _Model.LastName = value; 
        }
    }
    public string FullName
    { 
        get 
        { 
            return _Model.FirstName + " " _Model.LastName; 
        }
    }

    //Through this property you will always access current model property
    //without conversions
    public Person Model { get { return _Model; }}
}

//ViewModel which used as DataContext in the View
class PersonViewModel
{
    private PersonModelWrapper _Wrapper;
    public string Wrapper
    { 
        get 
        { 
            return _Wrapper; 
        }
        set 
        {
            _Wrapper = value; 
        }
    }
}

EDIT 作为对@Mark Feldman 评论的回答
如果 wrapper 看起来没有必要或代码臃肿，则可以跳过“ModelWrapper”，INotifyPropertyChanged 可以由 Model 本身实现。 如果您不关心模型属性更改的通知视图，那么您不需要将模型集合转换为 ViewModel 集合。
您的 ViewModel 将包含 ObservableCollection 类型的属性

class PersonViewModel
{
    public ObservableCollection<Person> Persons { get; set; }

    //if you don't care about tracking changes of collection(Add, Remove)
    //then use only List<Person> without any conversions
   public List<Person> Persons { get; set; }

}

没有包装器的视图模型

public class PersonViewModel: INotifyPropertyCahnged
{
    private Person _Model;
    public Person Model
    {
        get { return _Model; }
        set
        {
            if(Equals(_Model, value) == true)
               return;
            _Model = value;
            this.RaisePropertyChanged();
        }

        public String FullName {get {return _ModelFirstName + " " + _Model.LastName; }}

        public PersonViewModel(Person model)
        {
            _Model = model;
        }
    }
}

然后通过构造函数将模型列表转换为视图模型的集合以同样的方式发生