如何使用LINQ检索列表中包含一个列表的多个属性的条目？

Question

我有一个IJapaneseDictionaryEntry对象的列表，如下所述。 这里面是IKanji包含对象Priorites对象。

我有一件很困难的事情想做，并且希望得到任何建议。 我想这样做的是检索有有一个入口项Priority “频率1”的具有Priority “频率2”或Priority从列表“Frequency3”的entries ，我创建的。

public interface IJapaneseDictionaryEntry
{
    int Sequence { get; }
    IEnumerable<IKanji> Kanjis { get; }
    IEnumerable<IReading> Readings { get; }
    IEnumerable<ISense> Senses { get; }
}

每个对象都包含IKanji对象的列表

public interface IKanji
{
    string Text { get; }
    IEnumerable<KanjiInformation> Informations { get; }
    IEnumerable<Priority> Priorities { get; }
}

这是清单：

List<IJapaneseDictionaryEntry> entries = dictionary.GetEntries().ToList();

我认为以下观点可能有助于解释内容：

我希望这里的信息足够，因为似乎很难解释我需要检索的内容。

Answer 1

var result = entries.Where(e => e.Kanjis.Any(k => k.Priorities.Contains(Priority.Frequency1) ||
k.Priorities.Contains(Priority.Frequency2) ||
k.Priorities.Contains(Priority.Frequency3)
)).ToList();

考虑到您的两个问题，我会做这样的事情：

[Flags]
public enum Priority
{
     Frequency1 = 1,
     Frequency2 = 2,
     Frequency3 = 4,
     Frequency4 = 8
}

public interface IKanji
{
    string Text { get; }
    IEnumerable<KanjiInformation> Informations { get; }
    Priority Priorities { get; }
}

在上面的示例中，将每个Priority视为int中的某个bit ，您可以使用按位或（ | ）添加优先级：

优先级= Priority.Frequency1 | Priority.Frequency2 //表示同时具有两个优先级

要检查它是否具有特定的优先级，请按位和（ & ）使用：

if((Priorities & Priority.Frequency1) == Priority.Frequency1
{
     // it contains Priority.Frequency1
}

然后，您正在寻找的答案将是：

Priority p = Priority.Frequency1 | Priority.Frequency2 | Priority.Frequency3

var result = entries.Where(e => e.Kanjis.Any(k => k.Priorities & p == p)))
.ToList();

Answer 2

这可能是一种解决方案：

var filteredEntries = entries.Where( // Only entries
    e => e.Kanjis.Any( // which have one or more kanjis with..
        a => a.Priorities.Any( // which have one or more priorities                    
            p => p.Value == "Frequency1" // which have a value of "Frequency1"
            )));

我将您的interfaces更改为classes以使其与某些示例数据一起运行：

public class IJapaneseDictionaryEntry
{
    public int Sequence { get; set; }
    public IEnumerable<IKanji> Kanjis { get; set; }
}
public class IKanji
{
    public string Text { get; set; }
    public IEnumerable<Priority> Priorities { get; set; }
}

public class Priority
{
    public string Value { get; set; }
}

public static void Main(string[] args)
{
    // Initialize 3 objects. One has Priority we're searching
    List<IJapaneseDictionaryEntry> entries = new List<IJapaneseDictionaryEntry>()
    {
        new IJapaneseDictionaryEntry(){ Sequence = 1, Kanjis = new List<IKanji>() { new IKanji() { Priorities = new List<Priority>() { new Priority() { Value = "Frequency1" } } } } },
        new IJapaneseDictionaryEntry(){ Sequence = 2, Kanjis = new List<IKanji>() { new IKanji() { Priorities = new List<Priority>() { new Priority() { Value = "Frequency2" } } } } },
        new IJapaneseDictionaryEntry(){ Sequence = 3, Kanjis = new List<IKanji>() { new IKanji() { Priorities = new List<Priority>() { new Priority() { } } } } },
    };

    // Here's the magic:
    var filteredEntries = entries.Where( // Only entries
        e => e.Kanjis.Any( // which have one or more kanjis with..
            a => a.Priorities.Any( // which have one or more priorities                    
                p => p.Value == "Frequency1" // which have a value of "Frequency1"
                )));

    // Let's check the output
    foreach (var e in filteredEntries)
    {
        Console.WriteLine(e.Sequence);
    }
}