[IronPython] Are Converters (IValueConverter) supported in IronPython + Silverlight?

Jimmy Schementi Jimmy.Schementi at microsoft.com
Thu Jan 21 06:52:42 CET 2010

Are you using clrtype.py or a C# stub? If you're not using either of these, then you will get a AG_E_PARSER_BAD_TYPE when trying to tell XAML about your Python type, since the corresponding CLR type won't be found. If send your python and XAML code, then I can help you figure this out.


On Jan 20, 2010, at 8:32 PM, Edward J. Stembler wrote:
> I installed the Developer runtime, which incidentally is LinkID=150227 for
> Mac.  In any case, I got my Converter recognized as a .NET type; however I
> couldn't get passed the AG_E_PARSER_BAD_TYPE error when loading the converter
> reference in XAML. I initially thought there may be some namespace issue, but
> I can see the Converter is reflecting it's correct namespace, and the XML
> namespace seems to match too.  I tried importing my converted in App.py
> before the XAML is loaded to see if that would put it in scope, but that
> didn't work either.  I'm not sure what to try next?  Anyone have any ideas?
> On Jan 20, 2010, at 3:12 AM, Jimmy Schementi wrote:
> >> I took a simple converter and ported it to IronPython, however
> >> I'm getting the ever helpful SystemError 2255.
> >
> > Do you have the Silverlight "Developer" runtime? The "Consumer" runtime
> give you only error codes, while the developer runtime gives you actual
> exception messages. Here's the developer runtime:
> > http://go.microsoft.com/fwlink/?LinkID=150228
> >
> >> I can manually import my converter class via the REPL, and do a dir on it
> too.
> >>  Which leads me to believe there's another issue I'm unaware of.
> >> Perhaps it's not supported?  Has anyone else tried implementing a
> >> converter in IronPython yet?
> >
> > IValueConverter is an interface that allows you to make custom data
> conversions that happen during data binding in XAML:
> http://msdn.microsoft.com/en-
> us/library/system.windows.data.ivalueconverter(VS.95).aspx. However,
> IronPython doesn't directly support data binding in Silverlight, since Python
> classes are not 1-to-1 with CLR classes. The XAML required to hook up a
> converter (Converter={StaticResource FormatConverter}) won't be able to find
> a FormatConverter class defined in IronPython either, since the name is auto-
> generated. So, you'll be able to interact with your Python classes from the
> REPL, but they will fail to be used in XAML (if you use the developer runtime
> you'll probably see an error in the XAML parser ... which unfortunately also
> gives cryptic error msgs =P)
> >
> > There are two ways to wire this up:
> >
> > (1) Use clrtype.py to control the CLR type, properties, etc, that the
> IronPython class generates. Lukáš Čenovský recently showed that you can do
> data-binding with this in Silverlight: http://gui-
> at.blogspot.com/2009/11/inotifypropertychanged-and-databinding.html
> >
> > (2) Have anything your XAML needs to reference as a C# stub (defining all
> things requiring static references, including properties and methods), which
> your Python class inherits from and defines the actual behavior.
> >
> > I suggest #1 as it's a more elegant solution, but #2 will work as a good
> safety net if you encounter something that doesn't work in #1.
> >
> > ~Jimmy
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