如何将字典转换为ConcurrentDictionary？

Question

我已经看到如何将ConcurrentDictionary转换为Dictionary,但我有一个字典,并希望转换为ConcurrentDictionary.我该怎么做？...更好的是,我可以将link语句设置为ConcurrentDictionary吗？

var customers = _customerRepo.Query().Select().ToDictionary(x => x.id, x => x);

Answer 1

使用 可以接受字典对象的ConcurrentDictionary<TKey, TValue> Constructor (IEnumerable<KeyValuePair<TKey, TValue>>)构造函数,如:

Dictionary<int, string> dictionary = new Dictionary<int, string>();
dictionary.Add(1,"A");
dictionary.Add(2, "B");

ConcurrentDictionary<int,string> concurrentDictionary = 
             new ConcurrentDictionary<int, string>(dictionary);

我可以将LINQ语句设置为ConcurrentDictionary吗？

不,你不能..ConcurrentDictionary 在LINQ中没有可用的创建扩展方法.您可以创建自己的扩展方法,也可以ConcurrentDictionary在投影结果时使用LINQ查询中的构造函数.

Answer 2

为什么不编写自己的扩展方法：

  public static class ConcurrentDictionaryExtensions {
    public static ConcurrentDictionary<TKey, TElement> ToConcurrentDictionary<TSource, TKey, TElement>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector, IEqualityComparer<TKey> comparer) {
        if (source == null) throw new ArgumentNullException("source");
        if (keySelector == null) throw new ArgumentNullException("keySelector");
        if (elementSelector == null) throw new ArgumentNullException("elementSelector");

        ConcurrentDictionary<TKey, TElement> d = new ConcurrentDictionary<TKey, TElement>(comparer ?? EqualityComparer<TKey>.Default);
        foreach (TSource element in source)
            d.TryAdd(keySelector(element), elementSelector(element));

        return d;
    }

    public static ConcurrentDictionary<TKey, TSource> ToConcurrentDictionary<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector) {
        return ToConcurrentDictionary<TSource, TKey, TSource>(source, keySelector, IdentityFunction<TSource>.Instance, null);
    }

    public static ConcurrentDictionary<TKey, TSource> ToConcurrentDictionary<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer) {
        return ToConcurrentDictionary<TSource, TKey, TSource>(source, keySelector, IdentityFunction<TSource>.Instance, comparer);
    }

    public static ConcurrentDictionary<TKey, TElement> ToConcurrentDictionary<TSource, TKey, TElement>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector) {
        return ToConcurrentDictionary<TSource, TKey, TElement>(source, keySelector, elementSelector, null);
    }

    internal class IdentityFunction<TElement> {
        public static Func<TElement, TElement> Instance
        {
            get { return x => x; }
        }
    }

}

简单地采用了.Net 框架中的代码。