字典如何实现Add(KeyValuePair)

Question

IDictionary<TKey, TValue>从接口扩展ICollection<KeyValuePair<TKey, TValue>>,所以它有一个Add(KeyValuePair<TKey, TValue> item)方法:

IDictionary<string, object> dic = new Dictionary<string, object>();
dic.Add(new KeyValuePair<string, object>("number", 42)); // Compiles fine

但是,尽管是Dictionary<TKey, Tvalue>implements IDictionary<TKey, TValue>,它没有这个方法重载:

Dictionary<string, object> dic = new Dictionary<string, object>();
dic.Add(new KeyValuePair<string, object>("number", 42)); // Does not compile

怎么会这样？

Answer 1

正如您在文档和参考源中看到的那样,明确地Dictionary<TKey, TValue>实现了ICollection<KeyValuePair<TKey, TValue>>接口的这一部分.

void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> keyValuePair) 
{
    Add(keyValuePair.Key, keyValuePair.Value);
}

正如您所发现的那样,您只能通过强制转换为IDictionary<TKey, TValue>或来调用它ICollection<KeyValuePair<TKey, TValue>>.

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