<p>I've found a answer how to remove diacritic characters on stackoverflow, but could you please tell me if it is possible to change diacritic characters to non-diacritic ones?</p>

<p>Oh.. and I think about .NET (or other if not possible)</p>

Copying from
my own answer to another question
:
Instead of creating your own table, you could instead convert the text to normalization form D, where the characters are represented as a base character plus the diacritics (for instance, "á" will be replaced by "a" followed by a combining acute accent). You can then strip everything which is not an ASCII letter.
The tables still exist, but are now the ones from the Unicode standard.
You could also try NFKD instead of NFD, to catch even more cases.
References:
http://unicode.org/reports/tr15/
http://www.siao2.com/2005/02/19/376617.aspx
http://www.siao2.com/2007/05/14/2629747.aspx