System.Drawing.Graphings.SmoothingMode getter throws ArgumentException "Parameter is not valid"

Question

I have a large and resource intensive C# GUI application which uses the DotNetBar 3rd party UI library.

Occasionally, it fails with the following exception and call stack:

====================================
 ERROR 
====================================
Exception type: ArgumentException
Parameter is not valid.

====================================
 CALL STACK 
====================================
   at System.Drawing.Graphics.get_SmoothingMode()
   at DevComponents.DotNetBar.⍜.PaintCaptionBackground(FormCaptionRendererEventArgs e)
   at DevComponents.DotNetBar.Rendering.Office2007Renderer.DrawFormCaptionBackground(FormCaptionRendererEventArgs e)
   at DevComponents.DotNetBar.OfficeForm.ὀ(Graphics ٠)
   at DevComponents.DotNetBar.OfficeForm.ᲀ()
   at DevComponents.DotNetBar.OfficeForm.WindowsMessageNCActivate(Message& m)
   at DevComponents.DotNetBar.RibbonForm.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

The call which is failing at the top of the stack is just accessing the SmoothingMode property, and property getters have no parameters, so it's a bit hard to know that the "Parameter is not valid" could mean.

This exception happens sporadically, it's not reproducible 100% of the time, but does seem to be associated with high resource usage within my application (it happens on loading a particular large "project" into the application) whereas other smaller projects do not trigger this, even though both large and small projects use the DotNetBar UI in the same way.

What would cause the SmoothingMode property to throw an ArgumentException?

Answer 1

Solved this, it turned out to be a case where object that owns the System.Drawing.Graphics object had been disposed.

In the DotNetBar library, DotNetBar.BufferedBitmap objects which are doing some low-level calls to allocate a bitmap, and then returning the Graphics using Graphics.FromHdc(IntPtr). If the BufferedBitmap was disposed before use, then all of the properties on the Graphics object would throw an exception when you try to access them.

The reason why the bitmap was being disposed before being used was complicated and a result of the interaction of my application with DotNetBar. In a nutshell: a WM_NCACTIVATE message triggered some code to redraw the window caption, but this caption-drawing code was triggering an OnPaint in my application, and indirectly triggering a WndProc that was processing another WM_NCACTIVATE, and thus calling the caption-drawing code underneath itself. One level of caption-drawing code was disposing the bitmap that the other level was not finished using.