how to use dictionary two way in c#

Question

public static Dictionary<int, string> dic = new Dictionary<int, string>() { 
            {1,"anystring1"},
            {2,"anystring2"}};

I need to use this

string str= dic[1]; // it is possible

int a=dic["anystring1"]; // My dream is it

Answer 1

Use another Dictionary<> and use it in reverse order of key/value.