For example you can use this

Code:
string numSeparator = 
CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator;
char numSepFromThis = (char)0;
char numSepToThis = (char)0;
if (numSeparator == ".") 
{
     numSepFromThis = ',';
     numSepToThis = '.';
}
else if (numSeparator == ",")
{
     numSepFromThis = '.';
     numSepToThis = ',';
...