Object reference not set to an instance of an object.

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Hi,

I've made an login page in asp.net, where a user logins and redirected to the page according to his permissions. Now, instead to write the permission code / verify the user's permission on each and every page, I wrote the code in the class named userpermission class. But when i try to run my web application, its showing me an error

"Object reference not set to an instance of an object."

Following is the code written in class

VB

Public Class userpermissions : Inherits System.Web.UI.Page

Public Sub nwperm()

Dim mymenu As Menu = Master.FindControl("NavigationMenu")  'Here I'm getting error

Dim mymi As MenuItem = mymenu.FindItem("TechnicalSupport")

mymi.Enabled =True

Dim mymenu2 As Menu = Master.FindControl("NavigationMenu")

Dim mymi2 As MenuItem = mymenu2.FindItem("Administrator")

mymi2.Enabled =True

Dim mymenuitem As MenuItem = mymi2.ChildItems(5)

mymenuitem.Enabled =True

End Sub

If i write the same code on each and every page of my application then its running fine, Idont know whats wrong in my class.

Code written in my login page:

VB

myTool.nwperm()

(Where myTool is declared as "Public myTool As New userpermissions")

Plz help me as I'm stuck here for last 2 days.

Thanks

Posted 5-Feb-12 19:52pm

mirzamujib

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Rajeev Jayaram 6-Feb-12 2:53am

This is a NullReferenceException. You are trying to use a reference variable who’s value is Nothing/null. Try yourself first to figure out where the value is null and why? Use break points/quick watch.

mirzamujib 6-Feb-12 2:58am

Thanks Rajeev..
Yeah you are right its a NullReferenceException. But how can i solve this issue.
If same code put on each page then its working fine.

Thanks again.

3 solutions

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Rajeev Jayaram · Answer 1 · 2012-02-05T20:07:00

Solution 1

Try this,

Dim mymenu As Menu = CType(Master.FindControl("YourContentPlaceHolderNameHere").FindControl("NavigationMenu"), Menu)

Posted 5-Feb-12 20:07pm

Rajeev Jayaram

Comments

mirzamujib 6-Feb-12 2:30am

Thanks Rajeev,

I tried but still same error on the same line.

Rajeev Jayaram 6-Feb-12 2:47am

Did you put your ContentPlaceHolder ID here, "YourContentPlaceHolderNameHere"?

mirzamujib 6-Feb-12 2:56am

yeah I put the contentplaceholder name as you showed above, but still same error.
Before my navigation menu was not inside the content place holder as its present on my master page. But I put my navigation menu on ContentPlaceHolder and tried and got the same error.

Rajeev Jayaram 6-Feb-12 3:04am

You have to use your ContentPlaceHolder ID and not this "YourContentPlaceHolderNameHere".

mirzamujib 6-Feb-12 3:23am

ok i'll try and let u know.
thanks

mirzamujib 6-Feb-12 3:25am

Yeah its ContentPlaceHolder ID but still same error...

Thanks Rajeev

mirzamujib 6-Feb-12 3:27am

I think there is something wrong in
Public Class userpermissions
Inherits System.Web.UI.Page

Because if i put the same code on each and every page its running fine. As each page inherits master page properties and my navigation menu is on master page.
Rajeev can you suggest me with the above description...

Thanks

bbirajdar 7-Feb-12 1:20am

Yes..Because this custom class inherits from Page class but does not inherit from MasterPage.. How in the world are you trying to access the Master page controls in it ???????/

Syed Salman Raza Zaidi · Answer 2 · 2012-02-05T20:08:00

Solution 2

Try this

C#

Master.FindControl("YourContentPlaceholderId").FindControl("NavigationMenu");

Hope this will help you

Posted 5-Feb-12 20:08pm

Syed Salman Raza Zaidi

Comments

mirzamujib 6-Feb-12 2:30am

Thanks Salman,

I tried but same error on the same line.

bbirajdar · Answer 3 · 2012-02-05T20:35:00

Solution 3

Step 1

Put a quickwatch on '

VB

Master.FindControl("YourContentPlaceholderId")

' and check if its null

Step 2

Then put a check on '

VB

Master.FindControl("YourContentPlaceholderId").FindControl("NavigationMenu");

' and cehck if it is also null.

Posted 5-Feb-12 20:35pm

bbirajdar

Updated 5-Feb-12 20:54pm

v2

Comments

mirzamujib 6-Feb-12 5:02am

Thanks for the reply...
I checked its showing null, but dont understand why its executing if i write the same code on each page of my asp.net.

bbirajdar 6-Feb-12 10:42am

Oh.. Got the issue.. You are inheriting the class from the Page class and this page class DOES NOT inherit from the Master. And the NavigationMenu is placed in the Master.

This is the reason.

bbirajdar 6-Feb-12 10:43am

try using,

this.Parent.Master.FindControl("YourContentPlaceholderId").FindControl("NavigationMenu");

and this.Parent.Parent.Master.FindControl("YourContentPlaceholderId").FindControl("NavigationMenu");

bbirajdar 6-Feb-12 10:45am

The best solution for you will be to write the above code in the Load event of master page instead of inherited basepage.

mirzamujib 7-Feb-12 2:51am

thanks Birajdar..
I'll try and let u know...
thanks again...

mirzamujib 7-Feb-12 3:01am

I tried but but there is no syntax like
me.parent.master (when I'm typing parent then . its not showing master as the next word)
I hope its clear

Thanks

bbirajdar 7-Feb-12 3:42am

I now found the issue....Because this custom class inherits from Page class but does not inherit from MasterPage.. You will not get any reference to Master Page and the controls in it...

You need to place the above code in Page_Load in Master page. NOT in the custom class

mirzamujib 7-Feb-12 3:49am

thanks Birajdar....
I'll try and let u know..

mirzamujib 7-Feb-12 3:53am

still same error...
I dont knw why its showing me error because the same code if i put in each page of my application, its working fine.
Thanks again...