urgent asp.net invalid cast error

[Guest]

System.InvalidCastException: Specified cast is not valid.
hi i am received that error below is my code

result = new CustID(Convert.ToString(reader["CustID"]),
Line 57:
(DateTime)reader["BirthDate"],Convert.ToString(reader["Name"]),
Convert.ToString(reader["Sex"]), (Byte)reader["NameFormatCodeOri"],
Convert.ToString(reader["Address"]),
Convert.ToString(reader["PostCode"]));
First error was can not convert dbnull to string then i used
Convert.tostring and now i am getting that error not with all record but with
some records i assume dbnull value created some problem
thanks

 

[Winista]

If some of your fields can have null values then you need to check for
DbNull values before accessing those values. You can convert a null value.

If (!Convert.IsDBNull(dr[......])
{
... do your stuff ...
}