User Control Instantiation Issue

ef1196 · December 12th, 2007, 04:52 PM

I have a UserControl Class that when loaded presents a NullReferenceException.

The control is instantiated twice in my main form as follows:

Code:

private CtrlPlayer Player1 = new CtrlPlayer(1);
private CtrlPlayer Player2 = new CtrlPlayer(2);

The UserControl displays in the Design Mode without a problem, and the program compiles fine as well.

While attempting to adhere to FxCop rules I have inadvertently made a change that has caused this issue, as the control previously worked.

I have spent several hours attempting to research this via Google and have not found a resolve.

I'll be glad to respond back with any further detail needed.

Best Regards,
Earl

dparsons · December 12th, 2007, 05:07 PM

What did you change per FxCop? Where is the exception being raised from?

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ef1196 · December 12th, 2007, 05:43 PM

Doug,

Thanks up front for assisting me with this one.

The changes made per FxCop would be lengthy to list as I am using it as a best practice guide. I did make changes regarding security and CLSCompliance, but both changes have been commented out and the situation persists. It is almost like the designer portion of the code is not being read.

Security changes to main form (commented out):

Code:

//[assembly: IsolatedStorageFilePermission(SecurityAction.RequestMinimum, UserQuota = 1048576)]
//[assembly: SecurityPermission(SecurityAction.RequestRefuse, UnmanagedCode = true)]
//[assembly: FileIOPermission(SecurityAction.RequestOptional, Unrestricted = true)]

CLSCompliant changes to CtrlPlayer UserControl (commented out):

Code:

//[assembly: CLSCompliant(true)]

A simple call to change the text of a groupbox on the control yields the exception. If I comment that line then the next line (and the next...) it will generate the famous "Object reference not set to an instance of an object" error on each subsequent line.

This one is not going to be easy to find (although the resolution probably will be).

Best Regards,
Earl

samjudson · December 13th, 2007, 05:17 AM

OK, firstly, none of the changes detailed above are changes to either the control or the form - they are all assembly properties, so it doesn't matter which source file they appear in.

Secondly, how many CtrlPlayer controls do you have on the form in design time? You create two in the code above, but then refer to it in the singular form later.

If the exception is being thrown when you try to change the groupbox text then either the user control is null, or the group box is null.

I notice you have a different constructor that is passes a number (i.e. CtrlPlayer(1)) - is this new constructor calling InitializeComponents() ?

/- Sam Judson : Wrox Technical Editor -/

ef1196 · December 13th, 2007, 10:42 AM

Thank You Sam,

As stated in the first post I thought the resolve would be easy. InitializeComponent() was not called in this constructor.

Best Regards,
Earl