Question

我有以下问题让我陷入困境。在下面的例子中，我创建了A类和B类，并从B类继承了A类。然后我创建了一个ObservableCollection<A>来保存一组人。我当时希望做的是扩展A类以包含B类中的属性，并将其创建为可以更新的引用副本ObservableCollection。

我遵守的错误是：

无法投射类型的对象 '<CastIterator>d__b1'1[iheriatance_obseravale_collection.Form1+B]'来类型 'System.Collections.ObjectModel.ObservableCollection'1[iheriatance_obseravale_collection.Form1+B]'。

public class A : INotifyPropertyChanged
{
    string _firstName;
    public string firstName
    {
        get
        {
            return _firstName;
        }
        set
        {
            if (_firstName != value)
            {
                _firstName = value;
                NotifyPropertyChanged("firstName");
            }
        }
    }

    string _surname;
    public string surname
    {
        get
        {
            return _surname;
        }
        set
        {
            if (_surname != value)
            {
                _surname = value;
                NotifyPropertyChanged("surname");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void NotifyPropertyChanged(string PropName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(PropName));
        }
    }
}

public class B : A, INotifyPropertyChanged
{
    bool _isSelected;
    public bool isSelected
    {
        get
        {
            return _isSelected;
        }
        set
        {
            if (_isSelected != value)
            {
                _isSelected = value;
                NotifyPropertyChanged("isSelected");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    public void NotifyPropertyChanged(string PropName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(PropName));
        }
    }
}

ObservableCollection<A> peopleColl = new ObservableCollection<A>();

private void addData()
{
    peopleColl.Add(new A() { firstName = "James", surname = "Smith" });
    peopleColl.Add(new A() { firstName = "John", surname = "Woods" });
}

ObservableCollection<B> selectedPeople;

private void selectAllPeople()
{
    selectedPeople = (ObservableCollection<B>)peopleColl.Cast<B>();

    foreach (B person in selectedPeople)
    {
        person.isSelected = true;
        Console.WriteLine("Surname:{0}, IsSelected:{1}", person.surname, person.isSelected);
    }
}

非常感谢 Stuart Turbefield

Answer 1

您必须迭代源，投射每个对象，然后创建一个新集合：

 selectedPeople = new ObservableCollection<B>(peopleColl.OfType<B>());

仅当peopleColl包含B个对象时才有效。如果它仅包含A，则需要从B创建A的新实例：

 selectedPeople = new ObservableCollection<B>(peopleColl.Select(i => new B(i));

public class B : A
{
    public B()
    {
    }

    public B(A a)
    {
       this.firstName = a.firstName;
       this.surname = a.surname;
    }
}

仅供参考，如果A实施INotifyPropertyChanged，而B继承自A，则无需再次INotifyPropertyChanged B 1}} class。

c＃将ObservableCollection转换为另一种类型

1 个答案: