Need help with an if statement, C#

As the title implies, I'm writing a pretty basic program to explore some of what I know.

It's a simple morse translator in C#, my question arises around this last issue I have with it.  I'm in the process of writing the converter from Morse to English

http://pastebin.com/VUCwtF0j

Line 273 is where the error occurs.  C# Express is telling me I'm trying to implicitly convert from string to a bool, anyone mind helping me with a different way to do this?

Is a bit of a silly mistake, but i think you'll live =)

pretty sure everyone who uses C/#/++ has done that at least twice ;)

Wonder if you could find a way to make it simpler // 400 lines of code is quite large, but otherwise it's good =)