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how to handle null

sir using ado i retrieve alues from a field like this

_ConnectionPtr con;
_RecordsetPtr rec;

con.CreateInstance(__uuidof(Conection));
con->Open() // to connect to the data source

rec.CreateInstance(__uuidof(Recordset));
rec->PutRefActiveConection(con);

rec->Open() // to open recordset using sql statement
               select emp_phone from employees

 Now this emp_phone field can contain NULL values also
 Then i use the following code to extract values from emp_phone

_variant_t v_phone;
v_phone=rec->GetCollect(L"emp_phone");

now this GetCollect() retrns value of type _variant_t which then gets stored in v_phone

then i use something like this

lstrcpy(str,(_bstr_t)v_phone)

and then i use str to show emp_phone's value

the point is that if emp_phone contains value
then lstrcpy() works fine

but if emp_phone's value is NULL
then if i use lstrcpy(str,(_bstr_t)v_phone)
the program gives error at run time
saying abnormal termination

so how should i find whether value in v_phone is null so that i dont use lstrcpy() in that case
0
chikersal
Asked:
chikersal
1 Solution
 
jhanceCommented:
if(v_phone != NULL){
  lstrcpy(str,(_bstr_t)v_phone);
}
0
 
chikersalAuthor Commented:
if(v_phone != NULL){
 lstrcpy(str,(_bstr_t)v_phone);
}

instead of this what i tried was

if(v_phone==NULL) MessageBox(hwnd,"Null Values","Message",MB_OK);

but it never displayed the dialog box.

but anyway thanks for it
i will try again
if it does not work i will get back to you
thanks
0
 
mirecCommented:
Hi chikersal,
have you tried:
if(v_phone.vt == VT_NULL) MessageBox(hwnd,"Null Values","Message",MB_OK);
?
I think that variant wrapper for NULL database values should have this type.

m.
0
 
NetminderCommented:
chikersal,

You have a large number of questions have been open for some time, and our records show you logged in as recently as today. Please resolve them appropriately as soon as possible. Continued disregard of your open questions will result in the force/acceptance of a comment as an answer; other actions affecting your account may also be taken. I will revisit these questions in approximately seven (7) days.

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Thanks,

Netminder
Community Support Moderator
Experts Exchange
0
 
NetminderCommented:
Force/accepted by

Netminder
Community Support Moderator
Experts Exchange
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