Question

我怀疑这个行为有一个术语，如果我知道的话，我可以谷歌并了解我需要的东西。但是，我不知道。

这是我的构造函数：

[Export(typeof(MainWindowViewModel))]
public class MainWindowViewModel : ObservableObject
{
    private readonly IProductService _productService;
    private readonly IProfileService _profileService;
    public IEnumerable<ProductViewModel> Products { get; private set; }
    private ProductViewModel _productSelected;

    [ImportingConstructor]
    public MainWindowViewModel(IProductService productService, IProfileService profileService, ILoggingService logger)
    {
        Products = _productService.InstalledProducts.Select(p => new ProductViewModel(p, _profileService, _logger));
        SelectTheProductInDirectoryRunningFrom();

        _productSelected.Load();
    }

    protected virtual void SelectTheProductInDirectoryRunningFrom()
    {
        string currentDir = Directory.GetCurrentDirectory();

        if (_productSelected != null && _productSelected.InstalledPath != null &&
                !_productSelected.InstalledPath.Contains(currentDir))
        {
            _productSelected =
                Products.Where(p => currentDir.Contains(p.InstalledPath)).Select(p => p).DefaultIfEmpty(
                    _productSelected).SingleOrDefault();
        }
    }

这似乎很明显。它构建了ProductViewModel s的集合，找到相关的集合，并在其上调用Load()。 ProductViewModel.Load()包含以下代码：

public class ProductViewModel : ObservableObject
{
    private readonly IProfileService _profileService;
    private readonly ILoggingService _logger;
    private ObservableCollection<ProfileViewModel> _profiles;
    private ConfigProfile _defaultConfig;
    private ProfileViewModel _currentProfile;
    public ListCollectionView Profiles { get; set; }

public bool Load(string errorMessage, bool critical)
{
    List<ProfileViewModel> profileVms = new List<ProfileViewModel> { _currentProfile };

    profileVms.AddRange(
        _profileService.GetSavedProfiles(_data.ProductType).Select(
            p =>
            {
                p.FilePath = current.FilePath;
                return new ProfileViewModel(p, _defaultConfig, _profileService) { IsChanged = false };
            }));
    _profiles = new ObservableCollection<ProfileViewModel>(profileVms);

    Profiles = new ListCollectionView(_profiles);
    Profiles.SortDescriptions.Add(new SortDescription("ProfileTypeValue", ListSortDirection.Ascending));
    Profiles.SortDescriptions.Add(new SortDescription("ProfileName", ListSortDirection.Ascending));
    Profiles.CurrentChanged += (sender, args) =>
    {
        ((ProfileViewModel)Profiles.CurrentItem).Initialize();
        _currentProfile = Profiles.CurrentItem as ProfileViewModel;
    };

    return true;
}

当我在visual studio调试器中逐步执行此代码时，所有内容都会执行，_profiles和Profiles都会正确分配。但是，当执行从MainWindowViewModel构造函数返回时，_profiles和Profiles都为空。

我按两次F11到达这里：

可能出现什么问题？我的物体是否以某种方式超出了范围？我想也许它与价值与参考有关，但我无法找到任何东西。谢谢！

Answer 1

从WhereSelectEnumerableIterator分配对象会创建一个新对象，因此原始列表未被更新。

_productSelected =
    Products.Where(p => currentDir.Contains(p.InstalledPath)).Select(p => p).DefaultIfEmpty(
        _productSelected).SingleOrDefault();

我在此次通话中添加了.ToList()

Products = _productService.InstalledProducts.Select(p => new ProductViewModel(p, _profileService, _logger));

将IEnumerable强制转换为List，而string s1 = "test"; string s5 = s1.Substring(0, 3)+"t"; string s6 = s1.Substring(0,4)+""; Console.WriteLine("{0} ", object.ReferenceEquals(s1, s5)); //False Console.WriteLine("{0} ", object.ReferenceEquals(s1, s6)); //True不会创建新对象并更新现有对象。谢谢@Igor。

一旦构造函数完成，对象就会消失

1 个答案: