Instead of using ParseExact, use TryParseExact:
string incorporate = "03 27,1954";
CultureInfo provider = CultureInfo.InvariantCulture;
DateTime dt;
if (!DateTime.TryParseExact(incorporate, "MM dd,yyyy", provider, DateTimeStyles.None, out dt))
{
... report problem to user ...
return;
}
string formatted = dt.ToString("yyyy-MMdd");