Null Refrence exception was unhandled by user..!

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C#

internal int GetIntValue(string element, bool canBeNull, bool canBeBlank)
{
    if (this._xd[this._topElement][element] == null)--------exception
    {
        if (!canBeNull)
        {
            throw new XmlElementMissingException(element);
        }
        return 0;

create exception !how to deal with !

Posted 28-Aug-14 4:22am

Naveen Singh

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[no name] 28-Aug-14 10:24am

You debug your code, find the object that is null, figure out why it's null when you expect it to be not null, fix your code.

Herman<T>.Instance 28-Aug-14 10:49am

try {google} catch {binq}....

Mike Meinz 28-Aug-14 10:58am

Either this._xd or this._topElement or element is null or several of them are null. You can add additional code to check whether any of these are null before executing the if statement that throws the exception.

Bernhard Hiller 29-Aug-14 2:57am

Zen software? if (this == null) { MessageBox.Show("Hello Nirwana!"); }

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Answer 1 · 2014-08-28T08:12:00

Please see the comment to the question my Mike Meinz.

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown. And you did not show what object supposed to be non-null was actually null.

Not to worry. This is one of the very easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferenced by using and of its instance (non-static) members, which requires this member/variable to be non-null, but in fact it appears to be null. Simply execute it under debugger, it will stop the execution where the exception is thrown. Put a break point on that line, restart the application and come to this point again. Evaluate all references involved in next line and see which one is null while it needs to be not null. After you figure this out, fix the code: either make sure the member/variable is properly initialized to a non-null reference, or check it for null and, in case of null, do something else.

Please see also: want to display next record on button click. but got an error in if condition of next record function "object reference not set to an instance of an object"[^].

Sometimes, you cannot do it under debugger, by one or another reason. One really nasty case is when the problem is only manifested if software is built when debug information is not available. In this case, you have to use the harder way. First, you need to make sure that you never block propagation of exceptions by handling them silently (this is a crime of developers against themselves, yet very usual). The you need to catch absolutely all exceptions on the very top stack frame of each thread. You can do it if you handle the exceptions of the type System.Exception. In the handler, you need to log all the exception information, especially the System.Exception.StackTrace:
http://msdn.microsoft.com/en-us/library/system.exception.aspx[^],
http://msdn.microsoft.com/en-us/library/system.exception.stacktrace.aspx[^].

The stack trace is just a string showing the full path of exception propagation from the throw statement to the handler. By reading it, you can always find ends. For logging, it's the best (in most cases) to use the class System.Diagnostics.EventLog:
http://msdn.microsoft.com/en-us/library/system.diagnostics.eventlog.aspx[^].

Good luck,

—SA

Null Refrence exception was unhandled by user..!

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Null Refrence exception was unhandled by user..!

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