System.nullreferenceexception issue in random();

Question

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Hi,

Am trying to generate random number and pass it from class a to class b with session

Class A

C#

public static void SendPwd(string Email)
{
    using (var client = new SmtpClient())
    {
        using (var message = new MailMessage(EmailFrom, Email))
        {
            Random rnd = new Random();
            var random = rnd.Next();
            if (random != null)
            {
                System.Web.HttpContext.Current.Session["random"] = random;
            }
            message.Subject = "Please Verify Your Account";
            message.Body = "<html><head><meta content=\"text/html; charset=utf-8\" /></head><body><p>Dear " + Email +
            ", </p><p>Please note the random Number and type in the Text box</p>" + "<p> Your Random Number is </p>" + random
            + "</a></p><div>Best regards,</div><div>Team</div><p>Do not forward "
            + "this email. The verify link is private.</p></body></html>";
            message.IsBodyHtml = true;
            client.EnableSsl = true;
            client.Send(message);
        };
    };
}

Class B

C#

var password = con.tblEmployees.Where(a => a.Emp_Email == user.EmailId).FirstOrDefault();
password.Emp_TempPwd = (int)HttpContext.Current.Session["random"];
con.SaveChanges();
return "success";

while am doing this I got this error

An exception of type 'System.NullReferenceException' occurred in ServerControl.dll but was not handled in user code

What I have tried:

I have searched in Google to find it but I can’t find solution so kindly help me to solve this issue
thanks in advance

Posted 28-Jun-16 0:41am

azkarriyaz

Updated 28-Jun-16 21:12pm

CHill60

v2

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Comments

CHill60 28-Jun-16 6:57am

And on which line did this exception occur?

azkarriyaz 29-Jun-16 1:14am

http://prntscr.com/bmgejz

Philippe Mori 28-Jun-16 10:10am

Obviously, you should use a debugger and should provide useful information if you want some help.

In your class B code, we have no idea of what is con. Also, have you verified that password is not null? You don't even tell us on which line the exception occurs.

As indicated in solution 1, it should be fairly easy to find the problem using a debugger...

azkarriyaz 29-Jun-16 1:14am

http://prntscr.com/bmgejz

azkarriyaz 29-Jun-16 1:15am

using (var con = new empEntities())

3 solutions

Solution 2

You did not show where the exception with the message "Object reference not set to an instance of an object" is thrown.

Not to worry. This is one of the easiest cases to detect and fix. It simply means that some member/variable of some reference type is dereferences 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

Posted 28-Jun-16 5:11am

Sergey Alexandrovich Kryukov

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OriginalGriff · Accepted Answer · 2016-06-28T01:00:00

This is one of the most common problems we get asked, and it's also the one we are least equipped to answer, but you are most equipped to answer yourself.

Let me just explain what the error means: You have tried to use a variable, property, or a method return value but it contains null - which means that there is no instance of a class in the variable.
It's a bit like a pocket: you have a pocket in your shirt, which you use to hold a pen. If you reach into the pocket and find there isn't a pen there, you can't sign your name on a piece of paper - and you will get very funny looks if you try! The empty pocket is giving you a null value (no pen here!) so you can't do anything that you would normally do once you retrieved your pen. Why is it empty? That's the question - it may be that you forgot to pick up your pen when you left the house this morning, or possibly you left the pen in the pocket of yesterdays shirt when you took it off last night.

We can't tell, because we weren't there, and even more importantly, we can't even see your shirt, much less what is in the pocket!

Back to computers, and you have done the same thing, somehow - and we can't see your code, much less run it and find out what contains null when it shouldn't.
But you can - and Visual Studio will help you here. Run your program in the debugger and when it fails, VS will show you the line it found the problem on. You can then start looking at the various parts of it to see what value is null and start looking back through your code to find out why. So put a breakpoint at the beginning of the method containing the error line, and run your program from the start again. This time, VS will stop before the error, and let you examine what is going on by stepping through the code looking at your values.

But we can't do that - we don't have your code, we don't know how to use it if we did have it, we don't have your data. So try it - and see how much information you can find out!

azkarriyaz · Accepted Answer · 2016-06-28T21:12:00

Solution 3

C#

protected void Application_PostAuthorizeRequest() 
{
System.Web.HttpContext.Current.SetSessionStateBehavior(System.Web.SessionState.SessionStateBehavior.Required);
}

add
to global.asax

Posted 28-Jun-16 21:12pm