I have a method returning a List, let\'s call it GetSomeStrings().
GetSomeStrings()
I have an extension method on string class, returning number of characters in the str
You need to use the overload of ToDictionary which takes two functions:
var myDic = GetSomeStrings().ToDictionnary(x => x, x => x.Number('A'));
Both functions take what ever object you are using to create the dictionary. The first produces the Key; the second, the Value.