在C#中将值和键从一个字典复制到另一个字典的最快方法是什么？

Dictionary<string, int> sourceDictionary = new Dictionary<string, int>
{
    { "apple", 1 },
    { "banana", 2 },
    { "orange", 3 }
};

Dictionary<string, int> targetDictionary = sourceDictionary.ToDictionary(x => x.Key, x => x.Value);