[Webinar] Streamline your web hosting managementRegister Today

x
?
Solved

retrieving data from a database smallint column that may be null

Posted on 2008-06-17
5
Medium Priority
?
497 Views
Last Modified: 2012-08-13
Hi

I don't program in c# so i hope you might be able to help me on this.

I need to retrieve data from a databse which is contained in a datareader. One of the columns in the reader, call it index 0, is of type smallint and it might have a value of null. what type of variable do i need to store this? Perhaps its nullable of int but i don't know how to use one of these in c#. Also how do i check the column value is not null before i retrieve it from the reader using something like myvar = reader.getInt16(0)

thanks a lot
andrea
0
Comment
Question by:andieje
  • 3
5 Comments
 
LVL 15

Accepted Solution

by:
crisco96 earned 2000 total points
ID: 21804152
Null from a database is different from the .Net null.

Null from a database will actual be System.Data.DBNull.

If you want to save the value from the reader to a variable do the following:
int? Value;
 
if(Reader[0] == System.Data.DBNull)
{
   Value = null;
}
else
{
   Value = Convert.ToInt32(Reader[0]);
}

Open in new window

0
 

Author Comment

by:andieje
ID: 21804394
hi, i tried that and got this error

Invalid attempt to read from column ordinal '4'.  With CommandBehavior.SequentialAccess, you may only read from column ordinal '5' or greater.
  if (reader[4] != DBNull.Value)
                            {
                               
                                subcontractorID = Convert.ToInt16(reader[4]);
                            }
                            else
                            {
                                subcontractorID = null;
                            }
                         
0
 

Author Comment

by:andieje
ID: 21804457
I CHANGED IT to this
   if (reader["subcontractorID"] != DBNull.Value)
                            {
                               
                                subcontractorID = Convert.ToInt16(reader[4]);
                            }
                            else
                            {
                                subcontractorID = null;
                            }
                         

thanks
0
 

Author Closing Comment

by:andieje
ID: 31467992
thanks
0
 
LVL 5

Expert Comment

by:Hendo1973
ID: 21804474
You could use Nullable types which would allow value types to have a null value assigned to them.
0

Featured Post

Never miss a deadline with monday.com

The revolutionary project management tool is here!   Plan visually with a single glance and make sure your projects get done.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In order to hide the "ugly" records selectors (triangles) in the rowheaders, here are some suggestions. Microsoft doesn't have a direct method/property to do it. You can only hide the rowheader column. First solution, the easy way The first sol…
Real-time is more about the business, not the technology. In day-to-day life, to make real-time decisions like buying or investing, business needs the latest information(e.g. Gold Rate/Stock Rate). Unlike traditional days, you need not wait for a fe…
Enter Foreign and Special Characters Enter characters you can't find on a keyboard using its ASCII code ... and learn how to make a handy reference for yourself using Excel ~ Use these codes in any Windows application! ... whether it is a Micr…
SQL Database Recovery Software repairs the MDF & NDF Files, corrupted due to hardware related issues or software related errors. Provides preview of recovered database objects and allows saving in either MSSQL, CSV, HTML or XLS format. Ensures recov…

590 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question