Object reference not set to an instance of an object

Question

1.00/5 (3 votes)

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Hi,

I am wondering this code(exe having this code) is working fine on my local machine, but when i use to run this code(exe having this code) on other machine I am getting this exception at run time.

Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object.<br />

Any help will be greatly appreciated.

here is my code:

do
       {
           HtmlElementCollection elc = el.Children;

               Id.CodeData = elc[0].InnerText;
               Id.StockData = elc[1].InnerText;
               Id.TypeData = elc[2].InnerText;
               Id.QuantityData = elc[3].InnerText;
               Id.PartData = elc[4].InnerText;
               Idata.Add(Id);
               el = el.NextSibling;

       } while (el!= null);

Posted 15-Apr-11 4:31am

shrikant003

Updated 15-Apr-11 4:34am

Tarun.K.S

v2

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Comments

Olivier Levrey 15-Apr-11 10:38am

What about the debugger?

8 solutions

Solution 2

Four possibilities:
1) Idata is not set to anything
2) Id is not set to anything
3) el is not set to anything
4) el has no children.

Assuming you have checked Idata, Id, and el, and that they are all valid, then re-code it a bit more defensively:

do
       {
           HtmlElementCollection elc = el.Children;
           if (elc != null)
               {
               Id.CodeData = elc[0].InnerText;
               Id.StockData = elc[1].InnerText;
               Id.TypeData = elc[2].InnerText;
               Id.QuantityData = elc[3].InnerText;
               Id.PartData = elc[4].InnerText;
               Idata.Add(Id);
               }
               el = el.NextSibling;

       } while (el!= null);

Posted 15-Apr-11 4:41am

OriginalGriff

Comments

shrikant003 15-Apr-11 11:12am

I tried my all possibilities, If supose el is havig 50 childrens and if I iterate up to 49 its executing fine , but its failing after the last children . i m wondering its not executing on other machine on my local machine everything is executing fine.

Solution 1

you should do this:

C#

while (el != null && el.HasChildren)
{
    HtmlElementCollection elc = el.Children;
    ...
    ...
}

You can also do this:

C#

while (el != null && el.Children.Count > 0)
{
    HtmlElementCollection elc = el.Children;
    ...
    ...
}

To retrieve the children, you should REALLY use key names instead of relying on there always being five of them, and in the expected order. You're doomed to fail if the data changes significantly.

Posted 15-Apr-11 4:40am

#realJSOP

Comments

shrikant003 15-Apr-11 11:13am

Count will remain same as it is a table i m parsing. I tried my all possibilities, If supose el is havig 50 childrens and if I iterate up to 49 its executing fine , but its failing after the last children . i m wondering its not executing on other machine on my local machine everything is executing fine.

#realJSOP 18-Jun-11 12:26pm

Of course, you care certainly free to ignore my advice. Good luck with your project.

Solution 3

Probably the HTML source isn't available on the other machine.

For situations where the condition can fail immediately you should use while. If something must execute at least once you can use do..while.

while (el!= null)
     {
         HtmlElementCollection elc = el.Children;

             Id.CodeData = elc[0].InnerText;
             Id.StockData = elc[1].InnerText;
             Id.TypeData = elc[2].InnerText;
             Id.QuantityData = elc[3].InnerText;
             Id.PartData = elc[4].InnerText;
             Idata.Add(Id);
             el = el.NextSibling;
      };

Good luck!

Posted 15-Apr-11 4:42am

E.F. Nijboer

Comments

shrikant003 15-Apr-11 11:11am

I tried my all possibilities, If supose el is havig 50 childrens and if I iterate up to 49 its executing fine , but its failing after the last children . i m wondering its not executing on other machine on my local machine everything is executing fine.

E.F. Nijboer 15-Apr-11 11:59am

Now you are still assuming that elc[] has 0..4 entries. You can check this out with the debugger using some breakpoints. It also looks like the data on the other machine is different that on your local machine you can also check this out. But you should make your code more robust and check array length as well before trying to accessing. For now, have a go with the debugger to check things out.

Solution 4

I suspect that this is happening when you index elc. You have hardcoded to index elc from 0 to 4, but you are not checking that elc.count > 4. Your code should look something like this:

while (el!= null && el.Children.Count > 4)
{
        HtmlElementCollection elc = el.Children;

        Id.CodeData = elc[0].InnerText;
        Id.StockData = elc[1].InnerText;
        Id.TypeData = elc[2].InnerText;
        Id.QuantityData = elc[3].InnerText;
        Id.PartData = elc[4].InnerText;
        Idata.Add(Id);
        el = el.NextSibling;

}

Posted 15-Apr-11 5:58am

Rick Shaub

Updated 15-Apr-11 7:03am

v2

Solution 6

Hi
I found the solution I put my code in try and catch block where I caught the exception and did nothing in catch block , now its working fine.

C#

try{
    do
    {
        HtmlElementCollection elc = el.Children;

            Id.CodeData = elc[0].InnerText;
            Id.StockData = elc[1].InnerText;
            Id.TypeData = elc[2].InnerText;
            Id.QuantityData = elc[3].InnerText;
            Id.PartData = elc[4].InnerText;
            Idata.Add(Id);
            el = el.NextSibling;

    } while (el!= null);

}
catch (Exception exp)
{
    //Console.WriteLine(exp.Message + "Failed here");
}

Posted 17-Apr-11 22:17pm

shrikant003

Updated 17-Apr-11 23:11pm

v2

Comments

BillWoodruff 28-Aug-11 1:33am

That's not a solution, I am afraid: that's sweeping the problem "under the rug." You got lots of great advice on this thread on how to figure out what's wrong: use it :)

Solution 7

i think this it true

C#

try{
                  do
                  {
                        HtmlElementCollection elc = el.Children;
                              Id.CodeData = elc[0].InnerText;
                              Id.StockData = elc[1].InnerText;
                              Id.TypeData = elc[2].InnerText;
                              Id.QuantityData = elc[3].InnerText;
                              Id.PartData = elc[4].InnerText;
                              Idata.Add(Id);
                              el = el.NextSibling;
                  } while (el!= null);
            }
            catch (Exception exp)
            {
                  //Console.WriteLine(exp.Message + &quot;Failed here&quot;);
            }

friv | friv 4

Posted 17-Apr-11 22:52pm

friv

Solution 11

I am testing these codes, hope it work :d

while (el!= null && el.Children.Count > 4)
{
        HtmlElementCollection elc = el.Children;

        Id.CodeData = elc[0].InnerText;
        Id.StockData = elc[1].InnerText;
        Id.TypeData = elc[2].InnerText;
        Id.QuantityData = elc[3].InnerText;
        Id.PartData = elc[4].InnerText;
        Idata.Add(Id);
        el = el.NextSibling;

}

Friv | Friv.com

Posted 30-Jun-11 18:37pm

Kevin Warwick

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-04-15T09:03:00

Please stop all this pointless guesswork. Run it under debugger and you will see very clearly what's wrong.
Also, there is no chance that it works differently on different machine; you need to reproduce things correctly, that's it. Also, stop your trial-and-error approach shown by your "I tried my all possibilities" note. You goal now is not make it working but reproduce how it is not working, to understand why. Use just two or three note.

The problem looks like very trivial. Get to work, set a breakpoint.

—SA

Object reference not set to an instance of an object

8 solutions

Solution 2

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Solution 1

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