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pelion
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Cannot access disposed object
Nov 11th, 2007 at 10:58pm
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Hi Stoyo,

A tricky one here,

I have a main application form which calls another form to display a chart. The form with the chart on it is global to the scope of the form, but if a user closes the chart form, then tries to reopen it I have to reinstansiate it as below

Code
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private void RefreshSolutionBuilderDialog()
        {
            if (dlgSolutionBuilder == null || dlgSolutionBuilder.IsDisposed)
            {
                dlgSolutionBuilder = new dlgSolutionBuilder(program, database);


Now when I use the chart on the dialog I am likely to get the following error
Quote:
Cannot access a disposed object.
Object name: 'FlowChart'.


The stack trace is too long for this mesage, but it starts

Quote:
at System.Windows.Forms.Control.CreateHandle()
at System.Windows.Forms.Control.get_Handle()
at System.Windows.Forms.Control.CreateGraphicsInternal()
at System.Windows.Forms.Control.CreateGraphics()
at MindFusion.Diagramming.WinForms.Box.xd1bdd0ee5924b59e()
at MindFusion.Diagramming.WinForms.Box..ctor(FlowChart parent)
at MindFusion.Diagramming.WinForms.FlowChart.CreateBox(Single x, Single y, Single width, Single height)
at


Any thoughts?
  
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Stoyo
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Re: Cannot access disposed object
Reply #1 - Nov 12th, 2007 at 6:13am
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Hi,

That looks like the problem discussed in this thread:
http://mindfusion.org/cgi/Forum/YaBB.pl?board=fcnet_brep;action=display;num=1187...

In short, make sure that all references to the closed forms, including event handlers raised from within the child forms but handled in the main form, or vice versa, are removed / detached. Otherwise, the disposed form might still raise some events or get some of its event handlers called. Disposing the form also disposes all child controls, including the flowchart. So when CreateBox tries to create a Graphics object, you get that exception.

I hope that helps,
Stoyan
  
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pelion
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Re: Cannot access disposed object
Reply #2 - Nov 12th, 2007 at 7:33pm
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I was working down that path, so I'll give it a bit of further work and see how it goes
  
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