invokemember.click - object reference not set to an instance of an object

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Hi
so i have this code

C#

htmlelement hmtl = webbrowser1.document.getelementbyid("id");

if (webbrowser1.documenttext.contains("whatever")
{
    html.invokemember("click")
}

but it comes back saying

object reference not set to an instance of an object

what can i do to correct this i have tried it in c sharp and vb and still the same error please help :)

Posted 4-May-13 6:35am

fatslice90

Updated 4-May-13 7:13am

Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ)

v3

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ExpertITM 4-May-13 13:01pm

what is webbrowser1?

Menon Santosh 4-May-13 13:18pm

check that the variable html is successfully initialized or not

[no name] 4-May-13 13:25pm

it has?

2 solutions

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Sergey Alexandrovich Kryukov · Answer 1 · 2013-05-10T10:30:00

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

This is the second time you ask about this exception. Apparently, you should not ask such questions again and again, but need to learn how to sort out such trivial issues by yourself.

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

Abhinav S · Answer 2 · 2013-05-04T07:30:00

Solution 1

Try debugging your source code.
html variable appears to be null.

Posted 4-May-13 7:30am

Abhinav S

Comments

[no name] 4-May-13 13:33pm

yes this is a problem.. please what can i do to change it to something else or to something that works i have tried for days to get this to work please help me

[no name] 4-May-13 18:28pm

any further help please :)

Abhinav S 5-May-13 4:12am

Check why html is null.

[no name] 5-May-13 14:30pm

i dont know why it is null thats why i am asking the question please help :)

Dave Kreskowiak 10-May-13 17:04pm

It's obivious really. You're code os looking for an element in the HTML document, called "id", and it's not being found, so the result returned in null.

Nobody can tell you anything more than this because we have no idea what you're doing, and apparently, neither do you.