.NET Framework 4 introduces a new method on its String class called IsNullOrWhiteSpace that checks whether a provided String is null, empty, or consists only of “white space.” This handy method is in ...

You should be using the tokenize to actually parse the sentences. If you tokenize on spaces then you can put spaces in where needed (between words) and not have to worry about 'removing' them.

The String.split methods can be very convenient for easily splitting a provided String based on a provided regular expression String. The only trick is figuring out a regular expression token to use ...