Error: Object reference not set to an instance of an object

Question

I'm develop an application using ASP.NET in c#, and I hit the following error:

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

and this is my code fragment:

Match matchNew = Regex.Match(parts[0].ToString(), @"([0]\.\d*)|[1]\.[0]$", RegexOptions.IgnoreCase);

It was testing in my local the code was perfectly fine, but it hit this error when moved the same code to my virtual environment.

I'm guessing maybe it is due to the dot net framework in my virtual environment.

Please help and thank you in advanced.

I'm more inclined to believe there is a problem with your code. — ChaosPandion
– ChaosPandion, Commented Sep 21, 2011 at 4:15
thank you for the respond, I manage to changed the code from parts[0].ToString() to parts[0] + "", then it work fine...please explain... — sams5817
– sams5817, Commented Sep 21, 2011 at 7:24

Sky Kelsey · Accepted Answer · 2011-09-21 06:27:09Z

4

Most likely parts[0] is null. This error is equivalent to a NullPointerException in Java.

Try setting a local variable to parts[0].ToString(); on the previous line, and see if the exception is thrown from that line instead.

I recommend only performing your match if you have something to perform it on:

if(parts[0] != null){
    Match matchNew = Regex.Match(parts[0].ToString(), @"([0]\.\d*)|[1]\.[0]$", RegexOptions.IgnoreCase);
}

edited Sep 21, 2011 at 6:27

answered Sep 21, 2011 at 4:15

Sky Kelsey

19.3k5 gold badges39 silver badges78 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Shannon Cornish · Accepted Answer · 2011-09-21 04:24:03Z

3

From the exception you're getting, it looks like either parts or parts[0] is null.

Perhaps consider introducing a variable for parts to see if that is null, and if so, handle either with a default value or display an error to the user, or throw an exception if that is appropriate in your situation.

object part = parts[0];
if (part == null)
{
    // part is null, either handle with default value or error.
}

Match matchNew = ...;

answered Sep 21, 2011 at 4:24

Shannon Cornish

9615 silver badges11 bronze badges

Comments

Bernesto · Accepted Answer · 2011-09-21 04:15:43Z

2

Most likely it is your array "parts" if its length is 0 then it will fail. Make sure to test it's length first.

answered Sep 21, 2011 at 4:15

Bernesto

1,45618 silver badges20 bronze badges

Comments

Danish Khan · Accepted Answer · 2011-09-21 06:33:00Z

1

replace the code by this :

if(parts != null && parts.Length>0)
{    

    if(parts[0] != null)
    {
       Match matchNew = Regex.Match(parts[0].ToString(), @"([0]\.\d*)|[1]\.[0]$", RegexOptions.IgnoreCase);
    }
}

and it would work fine. The array parts appears to be null in your case. But ideally you should also check if the array has elements and if the element in question is not null before you try to convert it to a string value.

answered Sep 21, 2011 at 6:33

Danish Khan

1,8915 gold badges22 silver badges36 bronze badges

Comments

Fahad Hussain · Accepted Answer · 2011-09-21 06:04:13Z

0

It seems that your array "parts" has no elements and therefore parts[0] is null and the exception occurs due to .ToString() because null can not be converted to string.

answered Sep 21, 2011 at 6:04

Fahad Hussain

1,1851 gold badge11 silver badges17 bronze badges

Collectives™ on Stack Overflow

Error: Object reference not set to an instance of an object

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related