[IronPython] Returning inherited classes to .NET

Howland-Rose, Kyle Kyle.Howland-Rose at aar.com.au
Sun Feb 24 15:47:04 PST 2008


Is there a good place to read about these variants?

________________________________

From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Curt
Hagenlocher
Sent: Monday, 25 February 2008 10:31 AM
To: Discussion of IronPython
Subject: Re: [IronPython] Returning inherited classes to .NET


It's a feature.  clr.AddReferenceToFile ends up calling
Assembly.LoadFile under the covers, which lets you load multiple
versions of the same assembly.  If this isn't the behavior you want, you
should use a differently variant of AddReference (such as
clr.AddReference).  Each variant has its uses; this one's don't
correspond well with your intentions.


On Sun, Feb 24, 2008 at 2:22 PM, Howland-Rose, Kyle
<Kyle.Howland-Rose at aar.com.au> wrote:


	Awesome, thanks Curt.  
	 
	Do you have any idea as to whether this is a bug or a feature?

________________________________

	From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Curt
Hagenlocher
	Sent: Saturday, 23 February 2008 1:33 AM
	To: Discussion of IronPython
	Subject: Re: [IronPython] FW: FW: FW: returning inherited
classes to .NET
	
	
	I built a test executable and was able to reproduce this.  And
when I changed 
	clr.AddReferenceToFile("WebControlLibrary.dll")
	to
	clr.AddReference("WebControlLibrary")
	it worked as expected.
	
	On Fri, Feb 22, 2008 at 6:02 AM, Curt Hagenlocher
<curt at hagenlocher.org> wrote:
	

		Ah, no.  I was thinking that you would modify your VB
code to launch it as a console app (for instance) rather than from
inside of ASP.NET <http://asp.net/>  -- and see if you still get the
same error. 


		On Thu, Feb 21, 2008 at 10:07 PM, Howland-Rose, Kyle
<Kyle.Howland-Rose at aar.com.au> wrote:
		

			Thanks for your help so late Curt (not that I
need a quick answer at all).
			 
			I am sure I am missing something big-time here
and "talking" as cross-purposes, but, to my mind the reason I don't have
a problem when running from the command line is because all I am doing
is running the ipy.exe on the file which loads some assemblies, creates
a class definition and a function definition and then terminates without
even instantiating the class.  Is this what you mean by "running it
directly"?   
			 
			Thanks again,
			Kyle

________________________________

			
			From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Curt
Hagenlocher
			
			Sent: Friday, 22 February 2008 4:55 PM
			To: Discussion of IronPython
			Subject: Re: [IronPython] FW: FW: returning
inherited classes to .NET
			
			
			If you're only getting the error under ASP.NET
<http://asp.net/> , then it's highly likely that you're loading multiple
copies of the same assembly, which is why the CLR can't cast your Python
class back to the VB base -- it literally considers them to be two
different classes.  This may be related to the way ASP.NET
<http://asp.net/>  makes shadow copies of your files, but there could be
other reasons as well (none of which, unfortunately, come to mind right
now).
			 
			Using an interface instead of a base class would
give you the same results.
			
			On Thu, Feb 21, 2008 at 9:44 PM, Howland-Rose,
Kyle <Kyle.Howland-Rose at aar.com.au> wrote:
			

				It runs fine from the command line but
then it does not do much ... yet.  For the moment I am simplifying it by
removing IP :(
				 
				I wanted to so some moderately heavy
reflection which to my thinking should be easier from IP but I will use
VB for now.  
				 
				I assume I *should* be able to return a
derived python class to VB?  Alternatively I could implement an
interface.  How can IP implement a .NET interface?
				(All pointers to pre-existing doco
warmly received :)
				 
				Thanks
				Kyle

________________________________

				
				From: users-bounces at lists.ironpython.com
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Curt
Hagenlocher
				
				Sent: Friday, 22 February 2008 4:29 PM
				To: Discussion of IronPython
				Subject: Re: [IronPython] FW: returning
inherited classes to .NET
				
				
				My apologies; I wasn't reading the code
correctly.  That's probably a sign that I should be going to bed. :)
Have you tried simplifying your version just a little bit by running it
directly rather than through ASP.NET <http://asp.net/> ?

				 
				On Thu, Feb 21, 2008 at 8:43 PM,
Howland-Rose, Kyle <Kyle.Howland-Rose at aar.com.au> wrote:
				

				Hi Curt,
				
				Thanks for replying.  When I view the
link I see the following:
				
				The .NET code creates the "Test" class
and then runs the python code
				which imports the "Test" class a
subclasses it to create python class
				"X".
				
				Class "X" is then called and cast to
type "Test" and assigned to the
				value obj.
				
				Is this what you are looking at?
				
				My code is pretty much identical.  The
VB looks like:
				
				
				Public MustInherit Class ChildControl
				   Public Function Control() As
WebControl
				       Return Nothing
				   End Function
				   Public Function GetValue() As String
				       Return Nothing
				   End Function
				   Public Function SetValue(ByVal value
As Object) As String
				       Return Nothing
				   End Function
				End Class
				
				Class IPReflection
				   Private Shared Instance As
IPReflection = Nothing
				   Private PyEngine As PythonEngine
				   Private PyModule As EngineModule
				
				   Public Shared Function Inst() As
IPReflection
				       If Instance Is Nothing Then
				           Instance = New IPReflection
				       End If
				       Return Instance
				   End Function
				
				   Private Sub New()
				       Dim path As String =
HttpContext.Current.Request.MapPath(".")
				       PyEngine = New PythonEngine
				       PyEngine.AddToPath(path)
				       PyModule = PyEngine.CreateModule
				       PyEngine.DefaultModule = PyModule
				
	
PyEngine.ExecuteFile(HttpContext.Current.Request.MapPath("CustomControls
				.py"))
				   End Sub
				
				   Public Function GetChildControl() As
ChildControl
				       Return
	
CType(Operations.Ops.Call(PyModule.Globals("GetControl")), ChildControl)
				   End Function
				End Class
				
				And the python looks like:
				
				import clr
				import sys
				
				clr.AddReference('System')
				import System
				
				sys.path.append(sys.path[0] + "/bin")
				
	
clr.AddReferenceToFile("WebControlLibrary.dll")
				clr.AddReference('System.Web')
				
				from System.Web.UI.WebControls import
Label
				
				from WebControlLibrary import
ChildControl
				
				class LabelChildControl(ChildControl):
				       def __init__(self):
				               self.control = Label()
				       def Control(self):
				               return self.control
				
				def GetControl():
				       return LabelChildControl()
				
				
				Thanks again,
				Kyle
				

				________________________________
				
				From: users-bounces at lists.ironpython.com
				
	
[mailto:users-bounces at lists.ironpython.com] On Behalf Of Curt
				Hagenlocher
				Sent: Friday, 22 February 2008 3:08 PM
				To: Discussion of IronPython
				Subject: Re: [IronPython] returning
inherited classes to .NET
				


				The page in question doesn't seem to
show what you describe -- deriving
				a Python class from a C# class.  Maybe
you could show us your sample
				code?
				
				
				On Thu, Feb 21, 2008 at 7:39 PM,
Howland-Rose, Kyle
				<Kyle.Howland-Rose at aar.com.au> wrote:
				
				
				       Hi all,
				       I am following
				
				
	
http://www.ironpython.info/index.php/Using_Python_Classes_from_.NET
	
<http://www.ironpython.info/index.php/Using_Python_Classes_from_.NET>
				but using VB.
				
				       In VB I declare a class and
derive a python 1.1 class from it
				but when I return it I get the
exception:
				
				       "Unable to cast object of type
	
'IronPython.NewTypes.WebControlLibrary.ChildControl_1' to type
				'WebControlLibrary.ChildControl'."
				
				       The page referenced above just
seems to cast the python class
				instance to the C# class instance but
this does not work for me in VB.
				
				       Any help would be appreciated :)
				
				       Thanks,
				
				       Kyle
				
				
				
				
	
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