c＃轉換運算符爲遞歸集合類

Question

我一直在努力獲得一個演員工作的類具有自己的集合。在使用List中具有兩個TypeA元素的根對象進行測試時，當List執行隱式轉換時...它將輸入集合的TypeA元素的轉換代碼，並且因爲這是樹的頂部，所以返回TypeAIntermediate無需進入foreach循環（即完美 - SomeAs中沒有任何內容）。但是當它返回轉換的實例時，它似乎重新開始在根的轉換代碼的頂部，就像什麼都沒有發生。

據我所知，這永遠不會停止。我重寫了這個遵循相同格式的簡化版本......希望我沒有搞砸。

//These are models used in a .Net 4.5 EF6 Library 
public class TypeA 
{ 
    public string TypeAStuff; 
    public TypeB JustOneB; 
    public List<TypeA> SomeAs; 


    public static implicit operator TypeAIntermediate(TypeA a) 
    { 
     //New up an Intermediate A to return. 
     TypeAIntermediate aI = new TypeAIntermediate(); 
     //And get ready to do handle the collection... a few ways to do this. 
     List<TypeAIntermediate> children = new List<TypeAIntermediate>(); 

     //...but this appears to create an infinite loop? 
     foreach (TypeA item in a.SomeAs) 
      children.Add(item); //Cast from TypeA to to TypeAIntermediate happens here but will just keeps cycling 

     aI.TypeAStuff = a.TypeAStuff; 
     aI.JustOneB = a.JustOneB; 
     aI.SomeAs = children; 
     return aI; 
    } 
} 

public class TypeB 
{ 
    public string TypeBStuff; 

    public static implicit operator TypeBIntermediate(TypeB b) 
    { 
     TypeBIntermediate bI = new TypeBIntermediate(); 
     bI.TypeBStuff = b.TypeBStuff; 
     return bI; 
    } 
} 

//These Intermediate Classes live in a .Net35 Library - Unity cannot use Libraries compiled for later .Net Versions. 
public class TypeAIntermediate 
{ 
    public string TypeAStuff; 
    public TypeBIntermediate JustOneB; 
    public List<TypeAIntermediate> SomeAs; 
} 

public class TypeBIntermediate 
{ 
    public string TypeBStuff; 
} 

Answer 1

下面是如何編寫該方法以避免堆棧溢出，如果您的層次結構中存在環路。

public static implicit operator TypeAIntermediate(TypeA a) 
{ 
    return Convert(a, new Dictionary<TypeA, TypeAIntermediate>()); 
} 

private static TypeAIntermediate Convert(
    Type A a, 
    Dictionary<TypeA, TypeAIntermediate> lookup) 
{ 
    TypeAIntermediate aI; 
    if(lookup.TryGetValue(a, out aI)) 
    { 
     return aI; 
    } 

    aI = new TypeAintermediate(); 
    lookup.Add(a, aI); 

    List<TypeAIntermediate> children = new List<TypeAIntermediate>(); 
    foreach (TypeA item in a.SomeAs) 
     children.Add(Convert(item, lookup)); 

    aI.TypeAStuff = a.TypeAStuff; 
    aI.JustOneB = a.JustOneB; 
    aI.SomeAs = children; 
    return aI; 
} 

基本上通過使用字典，你可以確定是否有任何TypeA對象已經爲它創造一個TypeAIntermediate對象在這種情況下，你不需要再次創建它，只是返回相應TypeAIntermediate參考。如果它沒有，那麼你創建一個新的TypeAIntermediate並填充它的集合遞歸調用Create方法，也需要字典。

此外，如果您在不同分支中有兩次相同的對象引用，則只會創建一個參考而不是兩個參考。