Jorge pointed out the other day that when we do a lot of string concatenation, it is better to use StringBuilder instead of the String class (e.g. str += "something more"; ). This is because StringBuilder gives a better performance when in memory than the standard String class, which requires garbage collection to remove.
A very good article of comparison: http://blog.briandicroce.com/2008/02/04/stringbuilder-vs-string-performance-in-net/
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