[IronPython] Question on instantiating a .NET class in Python and pass the instantiated object back to C#

[Samuel Tjokrosoesilo]

Sweet. I loaded them using the LoadAssembly in C# and voila the casting
works.

Thanks Curt for the prompt reply.

Samuel
On Thu, Jan 22, 2009 at 11:18 AM, Curt Hagenlocher <curt at hagenlocher.org>wrote:

> The error "unable to cast object of type X to type X" is generally the
> result of an assembly loader issue.  If you're using the hosting interface
> and want to get a reference to the hosting assembly, don't use
> "clr.AddReferenceToFile" -- you'll end up with the same assembly loaded
> twice.  I think "clr.AddReference" might be okay, but the best choice is for
> the hosting C# code to inject itself directly into the ScriptRuntime by
> saying something like this:
> runtime.LoadAssembly(typeof(CastTestObject).Assembly)
>
>   On Thu, Jan 22, 2009 at 8:59 AM, Samuel Tjokrosoesilo <samuelt at gmail.com
> > wrote:
>
>>   Forgive me if this has been asked before. I already went through the
>> archive and could not find any answer to this.
>>
>> Basically, the idea is to be able to define a class in C#.
>> Then in Python, make a reference to the C# library and instantiate an
>> object based on this class.
>> Then as requested by C# through IronPython, this object reference is then
>> passed back to be used/manipulated in C#.
>>
>> The error/issue I'm having is the casting of the object (passed from
>> Python) to the C# class. (last part of the code below)
>> Funny thing is that when I put a breakpoint on Visual Studio, I'm able to
>> cast these objects in the Watch Window, but only when the code actually runs
>> it fails with exception as below:
>>     Microsoft.Scripting.ArgumentTypeException: Expected
>> DLRProto1_Extensions.Test03.CastTestObject, got
>> DLRProto1_Extensions.Test03.CastTestObject
>>     Unable to cast object of type
>> 'DLRProto1_Extensions.Test03.CastTestObject' to type
>> 'DLRProto1_Extensions.Test03.CastTestObject'.
>>
>> I won't include the initialization of the engine and scope as they have
>> been taken care by the base class.
>>
>> // C# library
>>      public class CastTestObject
>>     {
>>         private int cnt;
>>         private int limit;
>>         public CastTestObject()
>>         {
>>             cnt = 0;
>>             limit = 1000;
>>         }
>>         public void IncrementCount()
>>         {
>>             cnt++;
>>         }
>>     }
>>
>> # Python script
>> import clr
>> clr.AddReferenceToFile("DLRProto1_Extensions.dll")
>> from DLRProto1_Extensions.Test03 import CastTestObject
>> cto = CastTestObject()
>> print cto
>> def returnTestObject():
>>  cto2 = CastTestObject()
>>  return cto2
>>
>> // C# code manipulation below
>> string script = ReadScript("Scenarios\\test03.py");
>> CompileAndExecute(script);
>>
>> CastTestObject ctoObject;
>> // does not work, but works in Watch Window in Debug Mode
>> ctoObject = ScrScope.GetVariable<CastTestObject>("cto");
>>
>> // cast does not work, but works in Watch Window in Debug Mode
>> object cObject = ScrEngine.Execute("returnTestObject()", ScrScope);
>> ctoObject = (CastTestObject) cObject; //fails here with the exception
>> above
>>
>> Any help is greatly appreciated.
>>
>> Thank you.
>>
>> Samuel
>>
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>>
>>
>
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