object reference not set to an instance of an object in vb.net error

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VB

Private Sub WebBrowser1_NewWindow(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles WebBrowser1.NewWindow


       Dim thiselement As HtmlElement = WebBrowser1.Document.ActiveElement

       Dim targeturl As String = thiselement.GetAttribute("href")

       e.Cancel = True
       Dim window As New Form1
       window.Show()
       window.WebBrowser1.Navigate(targeturl)


   End Sub

' I HAVE OPEN A NEW WEBBROWSER WINDOW IN VB.NET FORM AND I HAVE FOUND ERROR AT HREF

Posted 1-Oct-13 20:20pm

Member 10300796

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tanweer 2-Oct-13 2:32am

hi, try getting the element like this may solve your problem,
<pre lang="c#"> Dim thiselement As HtmlElement = WebBrowser1.Document.All.GetElementsByName("your element id here")</pre>

Member 10300796 4-Oct-13 5:43am

thanks but i have not element id contain it's take dynamic

Sergey Alexandrovich Kryukov 2-Oct-13 2:46am

In what line?
—SA

Member 10300796 4-Oct-13 5:42am

thanks but i have not element id contain

tanweer 4-Oct-13 5:52am

do you know the Text property of html Anchor Element inside your WebBrowser?

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Sergey Alexandrovich Kryukov · Accepted Answer · 2013-10-01T20:46:00

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 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