Object reference not set to an instance of an object

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I try to call a web service from the business Gateway of monster

C#

public void call()
        {
            System.Net.ServicePointManager.ServerCertificateValidationCallback +=
            (s, cert, chain, sslPolicyErrors) => true;

            com.monster.schemas.MonsterBusinessGatewayService gateway = new     MonsterBusinessGatewayService();
            RecruiterReferenceType rec = new RecruiterReferenceType();
            Job job = new Job();
            var r = rec.UserName = "xtestxftp";
            job.RecruiterReference.UserName = r;
            

            gateway.Url = "https://208.71.198.74:8443/bgwBroker";
            gateway.Credentials = System.Net.CredentialCache.DefaultCredentials;
            

            gateway.UpdateJob(job);
  
    }

But I encoutered this error "System.NullReferenceException: Object reference not set to an instance of an object."
Any help please

Posted 24-Mar-14 4:58am

amiach

Updated 24-Mar-14 5:03am

Krunal Rohit

v2

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Comments

Trajan McGill 24-Mar-14 11:06am

On what line are you encountering the error?

amiach 24-Mar-14 11:08am

In this line "job.RecruiterReference.UserName = r;"

ZurdoDev 24-Mar-14 11:12am

either RecruiterReference is null or UserName is null and needs to be instantiated with a new() first.

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Sergey Alexandrovich Kryukov · Accepted Answer · 2014-03-24T05:13:00

It means that job.RecruiterReference is null or, otherwise, job.RecruiterReference.UserName is null. Before this line, all you did was the call to the Job constructor. You did not show the code of this constructor, so we could not know what was initialized and what not.

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"[^].

You cannot ask such question every time you face this very usual problem. You need to lean how to sort out such things by yourself.

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