c# - 字典操作中add和[]有什么区别

Question

字典dict;

有什么区别

dict.add(key, value) 和 dict[key] = value

Answer 1

dict[key] = value 将在键不存在时添加值，否则它将用该(现有)键覆盖该值。

例子:

var dict = new Dictionary<int, string>();
dict.Add(42, "foo");
Console.WriteLine(dict[42]);
dict[42] = "bar";  // overwrite
Console.WriteLine(dict[42]);
dict[1] = "hello";  // new
Console.WriteLine(dict[1]);
dict.Add(42, "testing123"); // exception, already exists!