Determine whether the text is in Chinese or English

public  bool IsChineseCharacter (string str)
{
Regex regChina = new Regex ("^[^\x00-\xFF]");
Regex regEnglish = new Regex ("^[a-zA-Z]");

if (regEnglish.IsMatch (str)) {
return false;
}
else if (regChina.IsMatch (str)) {
return true;
}
else
{
return false;
}

//byte [] byte_len = System.Text.Encoding.Default.GetBytes (ch);
//if (byte_len.Length == 2) { return true; }

}