ConcurrentDictionary Lazy AddOrUpdate

Question

我發現這個擴展爲C＃將GetOrAdd轉換爲Lazy，並且我想爲AddOrUpdate執行相同的操作。

有人可以幫我將此轉換爲AddOrUpdate？

public static class ConcurrentDictionaryExtensions 
{ 
    public static TValue LazyGetOrAdd<TKey, TValue>(
     this ConcurrentDictionary<TKey, Lazy<TValue>> dictionary, 
     TKey key, 
     Func<TKey, TValue> valueFactory) 
    { 
     if (dictionary == null) throw new ArgumentNullException("dictionary"); 
     var result = dictionary.GetOrAdd(key, new Lazy<TValue>(() => valueFactory(key))); 
     return result.Value; 
    } 


} 

Answer 1

它是這樣的：

public static TValue AddOrUpdate<TKey, TValue>(this ConcurrentDictionary<TKey, Lazy<TValue>> dictionary, TKey key, Func<TKey, TValue> addValueFactory, Func<TKey, TValue, TValue> updateValueFactory) 
{ 
    if (dictionary == null) throw new ArgumentNullException("dictionary"); 
    var result = dictionary.AddOrUpdate(key, new Lazy<TValue>(() => addValueFactory(key)), (key2, old) => new Lazy<TValue>(() => updateValueFactory(key2, old.Value))); 
    return result.Value; 
} 

注意的第二個參數的格式：返回一個新Lazy<>對象的委託......所以從某個角度來看，雙懶惰： - ）