如何執行。在ObservableCollection中選擇Linq操作 <dynamic> 在C＃中

Question

我有一個ObservableCollection<dynamic>它包含一個ObservableCollection<MobileModel> 。 現在，我需要從ObservableCollection<dynamic>選擇“ 品牌屬性”

類文件是

public class Mobile
{
    private ObservableCollection<MobileModel> _mobileList;
    public ObservableCollection<MobileModel> MobileList
    {
        get { return _mobileList; }
        set { _mobileList = value; OnPropertyChanged(); }
    }

    public void GetMobile()
    {
        List<MobileModel> mList = new List<MobileModel>();
        List<MobileModelInfo> modList = new List<MobileModelInfo>();
        MobileModel mob = new MobileModel();

        modList.Clear();
        mob.Brand = "Apple";
        modList.Add(new MobileModelInfo { Name = "iPhone 4", Catagory = "Smart Phone", Year = "2011" });
        modList.Add(new MobileModelInfo { Name = "iPhone 5", Catagory = "Smart Phone", Year = "2013" });
        modList.Add(new MobileModelInfo { Name = "iPhone 6", Catagory = "Premium Smart Phone", Year = "2015" });
        mob.Model = new ObservableCollection<MobileModelInfo>(modList);
        mob.OS = "IOS";
        mList.Add(mob);

        mob = new MobileModel();
        modList.Clear();
        mob.Brand = "Samsung";
        modList.Add(new MobileModelInfo { Name = "S4", Catagory = "Smart Phone", Year = "2011" });
        modList.Add(new MobileModelInfo { Name = "S5", Catagory = "Smart Phone", Year = "2013" });
        modList.Add(new MobileModelInfo { Name = "S6", Catagory = "Ultra Smart Phone", Year = "2015" });
        mob.Model = new ObservableCollection<MobileModelInfo>(modList);
        mob.OS = "Android";
        mList.Add(mob);

        mob = new MobileModel();
        modList.Clear();
        mob.Brand = "MicroSoft";
        modList.Add(new MobileModelInfo { Name = "Lumina 9900", Catagory = "Phone", Year = "2011" });
        modList.Add(new MobileModelInfo { Name = "Opera X220", Catagory = "Smart Phone", Year = "2013" });
        mob.Model = new ObservableCollection<MobileModelInfo>(modList);
        mob.OS = "Windows";
        mList.Add(mob);

        mob = new MobileModel();
        modList.Clear();
        mob.Brand = "Sony Ericssion";
        modList.Add(new MobileModelInfo { Name = "S4", Catagory = "Smart Phone", Year = "2011" });
        modList.Add(new MobileModelInfo { Name = "S5", Catagory = "Smart Phone", Year = "2013" });
        modList.Add(new MobileModelInfo { Name = "S6", Catagory = "Ultra Smart Phone", Year = "2015" });
        mob.Model = new ObservableCollection<MobileModelInfo>(modList);
        mob.OS = "Android";
        mList.Add(mob);

        MobileList = new ObservableCollection<MobileModel>(mList);

        SelectBrand(new ObservableCollection<dynamic>(MobileList.Cast<dynamic>()), "Brand");

    }


    public void SelectBrand(ObservableCollection<dynamic> Source, string propertyName)
    {
        // How to Create perform the Select Operation for the Property "Brand" as specified in the second parameter "propertyName"

        List<string> BrandList = new List<string>();

    }

}

public class MobileModel : Notify
{
    private string _brand = string.Empty;
    private ObservableCollection<MobileModelInfo> _model = new ObservableCollection<MobileModelInfo>();
    private string _os = string.Empty;

    public string Brand
    {
        get { return _brand; }
        set { _brand = value; OnPropertyChanged(); }
    }
    public ObservableCollection<MobileModelInfo> Model
    {
        get { return _model; }
        set { _model = value; OnPropertyChanged(); }
    }

    public string OS
    {
        get { return _os; }
        set { _os = value; OnPropertyChanged(); }
    }
}

public class MobileModelInfo
{
    public string Name { get; set; }
    public string Catagory { get; set; }
    public string Year { get; set; }
}

Answer 1

我在這里不了解dynamic的用法。 據我了解的問題，除了指定屬性名稱而不是執行選擇器委托之外，您希望能夠實質上實現LINQ的Select() 。 由於屬性名稱在編譯時未知，因此我看不到dynamic會有什么幫助。

因此，暫時忽略dynamic ，您要問的是使用反射很簡單。 例如：

class A
{
    public string P { get; set; }
}

class Program
{
    static void Main(string[] args)
    {
        A[] rga =
        {
            new A { P = "One" },
            new A { P = "Two" },
            new A { P = "Three" },
        };

        foreach (string value in SelectProperty(rga, "P"))
        {
            Console.WriteLine(value);
        }
    }

    private static IEnumerable<string> SelectProperty<T>(IEnumerable<T> rga, string propertyName)
    {
        PropertyInfo pi = typeof(T).GetProperty(propertyName);

        foreach (T t in rga)
        {
            yield return (string)pi.GetValue(t);
        }
    }
}

請注意，在上面，因為我使用的是實際的元素類型而不是dynamic ，所以不必將我的集合包裝在該集合的全新副本中，並且可以直接訪問該類型的反射數據（即PropertyInfo ）通過編譯器語法，而不必深入研究實際傳遞給我的集合對象。

您應該能夠在代碼中使用類似的東西，並且可以通過直接傳遞MobileList對象引用來調用它。 例如：

List<string> brandList = SelectProperty(MobileList, "Brand").ToList();

對我來說似乎好多了。 :)