ダイナミックなlinqネストされたグループ

Question

ダイナミックネストされたグループはどのようにすることができますか？

result.GroupBy(f => f.level1) 
       .Select(l1 => new { 
        name = l1.Key, 
        children = l1.GroupBy(l2 => l2.level2) 
        .Select(l2 => new { 
         name = l2.Key, 
         children = l2.GroupBy(l3 => l3.level3) 
          .Select(l3 => new { 
           name = l3.Key, 
           children = new someObject() 
        }); 

がどのように私は、パラメータによって動的にグループを行うには、これを変更することができます。

letが、私はこの例を持っていると言います。 より深くから始めてください。

Answer 1

これを本当に動的に入れたいのであれば、レベルオブジェクトにレベル名を格納するのではなく、配列に入れて何らかの方法でループすることができます。

あなたが何をしたい扱うことができ、一般的なNestedGroupBy<> LINQの拡張メソッドを構築することができ、ことを言って、あなたはちょうどあなたが望むレベルごとにラムダを渡す必要があります：

// The NestedGroupBy<> extension method 
public static class LinqExtensions 
{ 
    public static IEnumerable<TTarget> NestedGroupBy<TSource, TTarget, TKey>(this IEnumerable<TSource> source, Func<TKey, IEnumerable<TTarget>, TTarget> factory, params Func<TSource, TKey>[] keySelectors) 
    { 
     return source.NestedGroupBy(factory, keySelectors, 0); 
    } 

    private static IEnumerable<TTarget> NestedGroupBy<TSource, TTarget, TKey>(this IEnumerable<TSource> source, Func<TKey, IEnumerable<TTarget>, TTarget> factory, Func<TSource, TKey>[] keySelectors, int selectorIndex) 
    { 
     // reached the end, just return an empty list 
     if(selectorIndex >= keySelectors.Length) 
     { 
      return new List<TTarget>(); 
     } 

     // do the GroupBy using the function at index selectorIndex in our list to find the key (level name) 
     // then call the factory to construct the target SomeObject, passing it the key and the recursive call to NestedGroupBy<> 
     return source.GroupBy(keySelectors[selectorIndex]) 
      .Select(f => factory(
       f.Key, 
       f.NestedGroupBy(factory, keySelectors, selectorIndex + 1) 
      ) 
     ); 
    } 
} 

// source object - assuming your result variable is List<LevelObject> 
public class LevelObject 
{ 
    public string level1 {get;set;} 
    public string level2 {get;set;} 
    public string level3 {get;set;} 

    public LevelObject(string level1, string level2, string level3) 
    { 
     this.level1 = level1; 
     this.level2 = level2; 
     this.level3 = level3; 
    } 
} 

// target object - what we will end up with in our final list 
// the constructor is optional - it just makes the NestedGroupBy<> call cleaner. 
public class SomeObject 
{ 
    public string name {get; set;} 
    public IEnumerable<SomeObject> children {get; set;} 

    public SomeObject(string name, IEnumerable<SomeObject> children) 
    { 
     this.name = name; 
     this.children = children; 
    } 
} 

// Sample code to use it. The JToken/JsonConvert call at the end just pretty prints the result on screen. 
public static void Main() 
{ 
    List<LevelObject> result = new List<LevelObject>() 
    { 
     new LevelObject("L1a1", "L2a1", "L3a1"), 
     new LevelObject("L1a1", "L2a2", "L3a1"), 
     new LevelObject("L1a1", "L2a1", "L3a2"), 
     new LevelObject("L1b1", "L2b1", "L3b1"), 
     new LevelObject("L1c1", "L2c1", "L3c1") 
    }; 

    /* old way - produces same result 
      var groupings = result.GroupBy(f => f.level1) 
        .Select(l1 => new SomeObject { 
         name = l1.Key, 
         children = l1.GroupBy(l2 => l2.level2) 
         .Select(l2 => new SomeObject{ 
          name = l2.Key, 
          children = l2.GroupBy(l3 => l3.level3) 
           .Select(l3 => new SomeObject{ 
            name = l3.Key, 
            children = new List<SomeObject>() 
           })})}).ToList(); 
    */ 

    var groupings = result.NestedGroupBy<LevelObject, SomeObject, string>(
     (key, children) => new SomeObject(key, children), 
     l => l.level1, l => l.level2, l => l.level3 
    ).ToList(); 

    Console.WriteLine(groupings.GetType()); 

    Console.WriteLine(JToken.Parse(JsonConvert.SerializeObject(groupings))); 
}