Q:

Case Sensitive Dictionary Keys

I've found plenty of info on the web about making dictionaries able to do case insensitive look-ups such that if I added a key/value pair of ("A", "value") calling
MyDict["a"] == MyDict["A"]

will return true.
What I want to know is why I get a "key has already been added" error when I do
MyDict.Add("A", "value1");
MyDict.Add("a", "value2");

if I defined my dictionary to do case sensitive look-ups. Is there no way to define a Dictionary to be able to add different cased keys?

A:

Dictionaries are case-sensitive by default - you don't need to do anything.
Dictionary<string, string> myDict = new Dictionary<string, string>();
myDict.Add("A", "value1");
myDict.Add("a", "value2");

See your code working online here: ideone.
If you are getting an error with your code then it's because one of those keys already exist in your dictionary.

A:

All Dictionaries are case-sensisitive. But you can use the case-insensitive string comparers provided by the StringComparer class to create dictionaries with case-insensitive string keys.
Check it from ideone.

