SqlDataReader sequential access appears to be advancing without being read

Question

I am currently facing a bizarre issue when running the following code on a single laptop (other environments are not experiencing the issue).

I create a SqlDataReader with CommandBehavior.SequentialAccess set, and attempt to read the first column of data.

using (SqlDataReader theReader = GetReader(theSQLConnection))
{
   if (theReader.HasRows && theReader.Read())
   {
      shortID = (short)theReader[MyConstants.SHORT_ID_COLUMN_NAME];
      ...

When my code runs, I get an error:

Attempt to read from column ordinal '0' is not valid. With CommandBehavior.SequentialAccess, you may only read from column ordinal '1' or greater.

However, if I put a breakpoint on the opening curly brace of the if statement, and then in the immediate window, type

(short)theReader[MyConstants.SHORT_ID_COLUMN_NAME]

then the value prints out in the immediate window as expected.

If I restart debugging and put the breakpoint on the shortID = ... line, then I get the exception message when trying the same thing in the immediate window.

It doesn't appear that there should be anything advancing the reader between the curly brace and the first read, but that is what the exception message is suggesting.

kuradac · Accepted Answer · 2015-08-27 20:51:06Z

2

The issue happens because you are in debug mode. When you are debugging make sure you have your Autos window closed. The Autos window automatically reads from the datareader when the statement is highlighted, thereby advancing your ordinal index. So when you execute the statement, the reader already advanced to the next ordinal.

answered Aug 27, 2015 at 20:51

kuradac

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Jack Gajanan · Accepted Answer · 2016-02-16 04:48:43Z

0

see - https://support.microsoft.com/en-us/kb/308614

you can access fields only once and in sequence of you SQL only

answered Feb 16, 2016 at 4:48

Jack Gajanan

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