After much struggling, I got this idea to work when running normally, but this approach fails when running under IIS.

I use GdipCreateBitmapFromHBITMAP to create a gdi+ bitmap from the handle given to me via Chart.CreateBitmap.

When this code runs normally I get a good new gdip bitmap handle and then I can save to file, but when it runs under IIS I get 0 from GdipCreateBitmapFromHBITMAP. Note that Chart.CreateBitmap DOES give me a proper handle, it just can't get converted to a gdip bitmap for some reason.

Does this give you a clue?

Great, so now we know where it fails. But why? And is there anything I can check or do to workaround it?

1. I don't think the size is an issue here because it worked when I loaded the same bitmap from a bmp file.

2. I checked the error code that it returns from GdipCreateBitmapFromHBITMAP : '2' which means 'invalid parameter' i think (if my internet search is correct).

Good/bad news:

I figured out what the problem is: Session 0 isolation. In Windows 2008/Vista/7, all services and IIS processes run in 'session 0' which has isolation from hardware devices, etc.

You can read about it here: http://msdn.microsoft.com/en-us/library/ff485857(v=vs.85).aspx

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This means that if your Chart runs inside a Windows Service or IIS, various GDI+ functions may fail, including saving to file. I tested it in a Windows Service and this is what happens.

This scenario is a huge problem, because people like me want to be able to create pictures from server-side components using your Chart component.


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Interesting news:

I found another workaround that first copies the bitmap byte array into a local Picture object (that is not linked to any GDI object/device), and then saves this picture object as a PNG using GDI+.

There may be a better/faster way to do this using Windows API - I don't know.

I wonder whether any other Chart functions don't work when using GDI+...

So, the ball is in your court now - I did everything I can. Please let me know if you find a way to make it work in the Chart. To test it, just run your app as a windows service in win2008.

I'm not sure what I did to get this new attitude. I actually thought I was helping you find a problem in your own software by debugging it for you. Silly me.

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No I didn't know. I never saw anything written on your web site to this effect when we bought it from you. And even now, when I look at the page for the ActiveX control, it says nothing about it not being compatible with server-side applications, nor does it mention the word 'desktop' in any page. Quite the opposite:

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Regarding 'active maintenance': We bought the Pro version of the control some time ago. I would have to check the purchase date to see if it is still active.

But, regardless, since this is an issue with your software that is advertised as working with any Windows application, I thought you would be pleased that I helped you find the cause. I guess not.

I understand why you wouldn't give this priority. I didn't mean to be pushy.

Until I figured out a workaround for using CreateBitmap, I thought I wouldn't have anti-aliasing because I would have to rely on the SaveToBitmap function instead. But the new workaround makes it workable.

By the way, the web scenario isn't the only one. As I mentioned, Windows services also don't work. So, for example, if you have a server that creates scheduled reports with a chart inside them and then saves or emails them, the same problem would occur. I had to implement the workaround for this case as well.