Modify a dictionary in a for loop in C# -

i experienced in c/c++ pretty newbie in c#. question pretty simple. have hash table integer keys , values , want increment values in hash table 1. prefer accomplish o(1) memory.

below 1 solution, which, opinion, somehow ugly. there other way make looks more decent?

        dictionary<int, int> dict = new dictionary<int, int>();         (int = 0; < dict.count; ++i)         {             dict[dict.keys.elementat(i)]++;         }  

ps: heard foreach read-only in c#. but, there way for(auto it& : dict) it.second++ in c++ can use still accomplish task in c#?

dictionary<,> doesn't provide way of doing - because updating value associated key counts change invalidates iterator. concurrentdictionary<,> does allow though, , has addorupdate method you:

using system; using system.linq; using system.collections.concurrent;  class test {     static void main()     {         var dict = new concurrentdictionary<int, int>         {             [10] = 15,             [20] = 5,             [30] = 10         };         foreach (var key in dict.keys)         {             dict.addorupdate(key, 0, (k, v) => v + 1);         }         console.writeline(string.join("\r\n", dict.select(kp => $"{kp.key}={kp.value}")));     } }