check whether the given value is string or not

public static bool IsNumeric(String strVal)
{
Regex reg = new Regex("[^0-9-]");
Regex reg2 = new Regex("^-[0-9]+$|^[0-9]+$");
return (!reg.IsMatch(strVal) && reg2.IsMatch(strVal));
}
-----------------------------

isNaN(objnumber)