>[I have not installed vs2010 on my new computer yet - so I cannot test]
>
>If you use a lot of mid() it will be slow. The reason is - I think - that each call creates another string (object)
>
>Can you use one char at a time ? If yes, why not index the string
>

>char c ;
>string s = "very long string";
>
>c = s[5];
>

We are talking at thousands of MID() which have to be done in a flash. The string is also in the range of 20k. So, I am not sure if this would be any better. This is a highly complex algorythm. The best would be to have the StringBuilder to include a Mid() function. But, this is not supported yet.