具有可观察集合的泛型方法

Question

这适用于使用 .Net 4.5 的 Windows 8.1 Store 应用

我发现自己为我拥有的每个“对象”复制了相同的代码。所以我试图创建一个更通用的方法来以我想要的方式获取所有数据。最初对我的不同对象来说，一切都是<Typed>，但现在我正在尝试使用通用的<Object>。

    public async Task<ObservableCollection<object>>selectAll()
    {
        var Items = await Win8StorageHelper.LoadData("person.dat", typeof(ObservableCollection<object>));
        ObservableCollection<object> ItemsList = new ObservableCollection<object>();
        if (typeof(Int32) == Items.GetType())
        {
            //Not Needed anymore
        }
        else
        {
            ItemsList = (ObservableCollection<object>)Items;
        }
        _list.Clear();
        foreach (object item in ItemsList)
        {
            _list.Add(item);
        }

        return _list;
    }

我有我原来的集合 _frequencyList，现在有一个新的通用集合 _list：

    private ObservableCollection<win8Chores.Model.databaseTables.Frequency> _frequencyList;
    public ObservableCollection<Object> _list = new ObservableCollection<Object>();

我正在尝试这样调用我的新方法：

_frequencyList = await selectAll();

但是，我收到一个错误：

不能隐式转换类型 'System.Collections.ObjectModel.ObservableCollection' 到 'System.Collections.ObjectModel>observableCollection'

我需要做什么才能使此代码正常工作？我什至走在正确的轨道上吗？任何帮助表示赞赏。

更新： 这些是我试图为通用示例重构的原始方法：

    public async Task<ObservableCollection<Person>> selectAllPersons()
    {
        var personItems = await Win8StorageHelper.LoadData("person.dat", typeof(ObservableCollection<Person>));
        ObservableCollection<Person> personItemsList = new ObservableCollection<Person>();
        if (typeof(Int32) == personItems.GetType())
        {
            //Not Needed anymore
        }
        else
        {
            personItemsList = (ObservableCollection<Person>)personItems;
        }
        _personList.Clear();
        foreach (Person item in personItemsList)
        {
            _personList.Add(item);
        }

        return _personList;
    }

    public async Task<ObservableCollection<Frequency>> selectAllFrequencies()
    {
        var frequencyItems = await Win8StorageHelper.LoadData("frequency.dat", typeof(ObservableCollection<Frequency>));
        ObservableCollection<Frequency> frequencyItemsList = new ObservableCollection<Frequency>();
        if (typeof(Int32) == frequencyItems.GetType())
        {
            //Not Needed anymore
        }
        else
        {
            frequencyItemsList = (ObservableCollection<Frequency>)frequencyItems;
        }
        _frequencyList.Clear();
        foreach (Frequency item in frequencyItemsList)
        {
            _frequencyList.Add(item);
        }
        return _frequencyList;
    }
    public async Task<ObservableCollection<Chore>> selectAllChores()
    {
        var choreItems = await Win8StorageHelper.LoadData("chore.dat", typeof(ObservableCollection<Chore>));
        ObservableCollection<Chore> choreItemsList = new ObservableCollection<Chore>();
        if (typeof(Int32) == choreItems.GetType())
        {
            //Not Needed anymore
        }
        else
        {
            choreItemsList = (ObservableCollection<Chore>)choreItems;
        }
        _choreList.Clear();
        foreach (Chore item in choreItemsList)
        {
            _choreList.Add(item);
        }
        return _choreList;
    }

Answer 1

我认为您应该为此使用泛型；见Introduction to C# Generics

public async Task<ObservableCollection<T1>> selectAll<T1>(string filename)
{
    var Items = await Win8StorageHelper.LoadData(filename, typeof(ObservableCollection<T1>));

    if (Items is ObservableCollection<T1>)
    {
         return ((ObservableCollection<T1>)Items).ToList();
    }
    else
    {
        // empty or not the right type; depending on what the storage helper gives us
        return new ObservableCollection<T1>();
    }
}

被调用

var personList = selectAll<Person>("person.dat");
var frequencyList = selectAll<Person>("frequency.dat");

Answer 2

你需要这样的东西

public async Task<ObservableCollection<T>> selectAllItems<T>(ObservableCollection<T> _list)
{
    var items = await Win8StorageHelper.LoadData(string.Format("{0}.dat",typeof(T).Name.ToLower()), typeof(ObservableCollection<T>));

    _list.Clear();
    if(!(items is ObservableCollection<T>))
    {
         return _list;
    }

    ObservableCollection<T> itemsList = (ObservableCollection<T>)items;        
    foreach (T item in itemsList)
    {
        _list.Add(item);
    }

    return _list;
}

_list是你需要添加所有项目的参数。

然后这样称呼它

selectAllItems(_personList);
selectAllItems(_frequencyList); //etc