.net - ConcurrentDictionary 惰性添加或更新

Question

我发现这个 C# 扩展将 GetOrAdd 转换为 Lazy，我想对 AddOrUpdate 做同样的事情。

有人可以帮我将其转换为 AddOrUpdate 吗？

 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

就是这个:

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;
}

注意第二个参数的格式:一个返回一个新的 Lazy<>的委托(delegate)。对象...所以从某种角度来看，它是双重懒惰的:-)