.Net Regular expression - how to do an exact match exclusion on a full string?

Question

I need a .Net regular expression that matches anything OTHER than the exact full string match specified. So basically:

^Index$

... is the only exclusion I care about. Strings can start with, finish with or contain "Index", but not match exactly. My brain doesn't seem to be working today and I'm failing to work this one out.

EDIT

The answer MUST be via the pattern itself, as I am passing an argument to a third party library and do not have control over the process other than via the Regex pattern.

Answer 1

If Regex is Must,

Match match = Regex.Match(input, @"^Index$");

if (!match.Success){
    //do something
}

And with horrible way

Match match = Regex.Match(input, @"^(.*(?<!Index)|(?!Index).*)$");

if (match.Success){
    //do something
}

_{Note: second one is not tested, and regex engine need to support full look ahead and look behind}

Answer 2

What about if (!r.Match("^Index$").Success) ...?

Answer 3

you can check !regex.Match.Success

Answer 4

That should do the trick:

^(?!Index$)