Solved

Loop Problem (Object Reference Problem)

Posted on 2003-12-08
6
422 Views
Last Modified: 2010-04-16
Hi.
My problem is simple, that's why i think the soulution won't be...

I Have this loop:

for( int y=0; y<oDS.Tables["Databases"].Rows.Count; y++ )
{
      oLI = new ListItem( oDS.Tables["Databases"].Rows[y]["TableCatalog"].ToString(), oDS.Tables["Databases"].Rows[y]["TableCatalog"].ToString() );
      dropDatabase.Items.Add( oLI );
}

It gave me a object reference error. But the quick watch shows "oDS.Tables["Databases"].Rows[y]["TableCatalog"]" with the prober value when I run the DEBUG.

Then I solved it with this:

string strTemp;

for( int y=0; y<oDS.Tables["Databases"].Rows.Count; y++ )
{
      strTemp = oDS.Tables["Databases"].Rows[y]["TableCatalog"].ToString();
      oLI = new ListItem( strTemp , strTemp );
      dropDatabase.Items.Add( oLI );
}

Why the hell the first one didn't worked out?

Thanks!
Roberto Colnaghi Junior
0
Comment
Question by:3DGames
6 Comments
 
LVL 18

Expert Comment

by:testn
ID: 9898623
Is tablecatalog field ntext or binary?
0
 

Author Comment

by:3DGames
ID: 9898761
It is a VARCHAR(64) SQL SERVER 2000 datatype.
0
 
LVL 20

Accepted Solution

by:
TheAvenger earned 125 total points
ID: 9899972
An interesting problem and it was probably not in the oDS.Tables["Databases"].Rows[y]["TableCatalog"] but in some other point...

Never mind, I would suggest you to change your code to something easier to read like:

foreach (DataRow row in oDS.Tables["Databases"].Rows)
{
     oLI = new ListItem(row["TableCatalog"].ToString(), row["TableCatalog"].ToString() );
     dropDatabase.Items.Add( oLI );
}

Try it then and see what happens
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 44

Expert Comment

by:Arthur_Wood
ID: 9904883
it would actually be BETTER (more efficient) to use somethig like this:

Sting  strRow as String;
foreach (DataRow row in oDS.Tables["Databases"].Rows)
{
     strRow = row["TableCatalog"].ToString();
     oLI = new ListItem(strRow,strRow);
     dropDatabase.Items.Add( oLI );
}

this makes a SINGLE call to the row["TableCatalog"].ToString() method, and 'caches' the result as strRow, which can then be used twice, rather than requiring the toString method to be executed twice.  This will be more efficient, performance wise.

AW

0
 
LVL 20

Expert Comment

by:TheAvenger
ID: 9904927
Arthur_Wood: 3DGames already made this but he had a problem when the calls to ToString were two (have a look at the above posts) so I suggested that he calls the ToString method again twice to see if there is any difference
0
 

Author Comment

by:3DGames
ID: 9911291
Well... Thanks for the solution!

But the question remains.... why my first loop didn't worked?

Your answer(TheAvenger) are almost the same as it...... Ok, it is much more clean and easier to read :) , but I think that both should work.
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
Achieve json result 2 64
COnsume rest client 6 34
Turn on intranet settings 1 36
Facial recognition to look through the whole database for a person 3 39
Exception Handling is in the core of any application that is able to dignify its name. In this article, I'll guide you through the process of writing a DRY (Don't Repeat Yourself) Exception Handling mechanism, using Aspect Oriented Programming.
It was really hard time for me to get the understanding of Delegates in C#. I went through many websites and articles but I found them very clumsy. After going through those sites, I noted down the points in a easy way so here I am sharing that unde…
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.
This is a video describing the growing solar energy use in Utah. This is a topic that greatly interests me and so I decided to produce a video about it.

932 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

Need Help in Real-Time?

Connect with top rated Experts

19 Experts available now in Live!

Get 1:1 Help Now