Programando na madrugada

public static String RemoveSpecialCharacters(this String self)
{
	var normalizedString = self;
 
	// Prepara a tabela de símbolos.
	var symbolTable = new Dictionary<char, char[]>();
	symbolTable.Add('a', new char[] {'à', 'á', 'ä', 'â', 'ã'});
	symbolTable.Add('c', new char[] { 'ç' });
	symbolTable.Add('e', new char[] { 'è', 'é', 'ë', 'ê' });
	symbolTable.Add('i', new char[] { 'ì', 'í', 'ï', 'î' });
	symbolTable.Add('o', new char[] { 'ò', 'ó', 'ö', 'ô', 'õ' });
	symbolTable.Add('u', new char[] { 'ù', 'ú', 'ü', 'û' });
 
	// Substitui os símbolos.
	foreach (var key in symbolTable.Keys)
	{
		foreach (var symbol in symbolTable[key])
		{
			normalizedString = normalizedString.Replace(symbol, key);
		}
	}
 
	// Remove os outros caracteres especiais.
	normalizedString = Regex.Replace(normalizedString, "[^0-9a-zA-Z._]+?", "");
	return normalizedString;
}