Can anyone help?

I am trying to retreive data from and Oracle 9i database using the .NET framework Data Provider for Oracle. The data is retreived through a "VIEW". The sql for the "VIEW" uses the NVL function to convert Null values into empty strings for some fields. After retreiving the data I am finding the fields that are suppose to be receiving the empty string are receiving DBNull values which in turn cause a "Cast" error trying to convert a DBNull to a string. Is there something I am not doing right that is giving me this error.

Thanks

JimB