empty string with ado

[StefanoCarniel]

Hello, I'm trying to read the value of the field PostalCode from an Access database using ado with the following sintax:

CString buff;

buff = pRecordsetAccess->Fields->GetItem ("PostalCode")->Value.bstrVal;

but if the field is empty (NULL value), I get an access violation error. I tried to use other sintax, like

....->Value.bVal;

in this case I do not get any error, but in buff I find a strange character and not an empty string. How can I manage this situation?

Thank you

 

[LazyMe]

That is because a NULL value in fact is not an empty string. You should first check for a NULL value and then try to assign it to your string buffer.

Greetings,
Rick

 

[LazyMe]

Maybe even better; have the query return an empty string in case of a NULL value. Don;t know if the same syntax can be used in an acces database, but somthing like ISNULL(PostalCode, '')...

Greetings,
Rick

 

[ArkM]

Try this approach in Access ADO apps:

inline bool isNull(const _variant_t& v)
{
       return v.vt == VT_NULL;
}
inline bool isNull(const ADODB::FieldPtr& p)
{
     return isNull(p->Value);//p->Value.vt == VT_NULL;
}

It works.