Bug 3739 - System.Data.SqlClient.SqlDataReader.IsDBNull is a read for Mono, not to MS
Summary: System.Data.SqlClient.SqlDataReader.IsDBNull is a read for Mono, not to MS
Status: NEW
Alias: None
Product: Class Libraries
Classification: Mono
Component: System.Data (show other bugs)
Version: unspecified
Hardware: PC Windows
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
URL:
Depends on:
Blocks:
 
Reported: 2012-03-02 20:26 UTC by arjan
Modified: 2012-03-02 20:26 UTC (History)
1 user (show)

Tags:
Is this bug a regression?: ---
Last known good build:

Notice (2018-05-24): bugzilla.xamarin.com is now in read-only mode.

Please join us on Visual Studio Developer Community and in the Xamarin and Mono organizations on GitHub to continue tracking issues. Bugzilla will remain available for reference in read-only mode. We will continue to work on open Bugzilla bugs, copy them to the new locations as needed for follow-up, and add the new items under Related Links.

Our sincere thanks to everyone who has contributed on this bug tracker over the years. Thanks also for your understanding as we make these adjustments and improvements for the future.


Please create a new report for Bug 3739 on GitHub or Developer Community if you have new information to add and do not yet see a matching new report.

If the latest results still closely match this report, you can use the original description:

  • Export the original title and description: GitHub Markdown or Developer Community HTML
  • Copy the title and description into the new report. Adjust them to be up-to-date if needed.
  • Add your new information.

In special cases on GitHub you might also want the comments: GitHub Markdown with public comments

Related Links:
Status:
NEW

Description arjan 2012-03-02 20:26:07 UTC
Description of Problem:

Small, but it made my application crash. I guess Mono is right about this and MS isn't, but may be Mono could be the wise party. Error is "invalid attempt tp read from column..."  (sic)

Steps to reproduce the problem:
1. Make a System.Data.SqlClient.SqlDataReader
2. Read
3. Test if field(0) is null with IsDBNull
4. Try to get the value of field(0)

like:
If DataReader.IsDBNull(i) Then
 bla
else
 msgbox (DataReader(i)) ' ordinal0 
end if

Actual Results:

Error, because you are reading the same field twice.

Expected Results:

Actually, what Mono does, but my application didn't like it. "Workaround" in VB something is something like:
 Dim obj As Object = DataReader(i)
 If TypeOf (obj) Is System.DBNull Then
  FieldValue = ""
 Else
  FieldValue = CStr(obj)
 End If

How often does this happen? 

Once until solved

Additional Information:

As the error message has a spelling error, the source is probably easy to find. "invalid attempt tp read from column".