How to iterate through Dictionary and change values?

Question

Dictionary myDict = new Dictionary();
//...
foreach (KeyValuePair kvp in myDict)
 {
     kvp.Value = Math.Round(kvp.Value,          


        

Answer 1

I noticed that fastest way (at this moment) iterate over Dictionary with modify is:

//Just a dumb class
class Test
{
    public T value;

    public Test() { }
    public Test(T v) { value = v; }
}

Dictionary> dic = new Dictionary>();
//Init dictionary
foreach (KeyValuePair pair in dic)
{
    pair.Value.value = TheObject;//Modify
}

VS

List keys = new List(dic.Keys); //This is fast operation   
foreach (int key in keys)
{
    dic[key] = TheObject;
}

First one takes about 2.2s and second one 4.5s (tested dictionary size of 1000 and repeated 10k time, changing dictionary size to 10 didn't change the ratios). Also there wasn't a big deal with getting the Key list, dictionary[key] value get is just slow VS built in iteration. Also if you want even more speed use hard coded type to dumb ("Test") class, with that I got it about 1.85s (with hard coded to "object").

EDIT:

Anna has posted the same solution before: https://stackoverflow.com/a/6515474/766304