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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Generic virtual method in baseclass causes InvalidProgramException","articleBody":"### Environment\r\n\r\n-   Pythonnet version: 3.0.0-preview2022-04-11\r\n-   Python version: 3.10\r\n-   Operating System: MacOS and Ubuntu 2021.4\r\n-   .NET Runtime: .net 6\r\n\r\n### Details\r\n\r\nIf I create a python class which inherits from a C# class that has a virtual generic method and exception is thrown while the class is being defined. Note, not during object instanciation time.\r\n\r\nTo reproduce, take the following C# class:\r\n```cs\r\n    public abstract class GenericVirtualMethodTest\r\n    {\r\n        public virtual Q VirtMethod\u003cQ\u003e(Q arg1)\r\n        {\r\n            return arg1;\r\n        }\r\n    }\r\n```\r\n\r\nThen inherit from it as in this test:\r\n\r\n```py\r\ndef test_virtual_generic_method():\r\n    class OverloadingSubclass(GenericVirtualMethodTest):\r\n        __namespace__ = \"test_virtual_generic_method_cls\"\r\n    obj = OverloadingSubclass()\r\n    assert obj.VirtMethod[int](5) == 5\r\n```\r\n\r\nThe result is the following exception (Actually a C# exception inside a python exception inside a C# exception):\r\n```\r\nPython.Runtime.PythonException : An attempt was made to load a program with an incorrect format.\r\n (0x8007000B)\r\n  File \"/Users/bruger/code/work/pythonnet/src/../tests/test_subclass.py\", line 268, in test_virtual_generic_method\r\n    class OverloadingSubclass(GenericVirtualMethodTest):\r\n  File \"\u003cstring\u003e\", line 19, in \u003cmodule\u003e\r\n   at Python.Runtime.PythonException.ThrowLastAsClrException() in /Users/bruger/code/work/pythonnet/src/runtime/PythonException.cs:line 53\r\n   at Python.Runtime.PythonException.ThrowIfIsNull(NewReference\u0026 ob) in /Users/bruger/code/work/pythonnet/src/runtime/PythonException.cs:line 455\r\n   at Python.Runtime.PythonEngine.RunString(String code, BorrowedReference globals, BorrowedReference locals, RunFlagType flag) in /Users/bruger/code/work/pythonnet/src/runtime/PythonEngine.cs:line 625\r\n   at Python.Runtime.PythonEngine.Exec(String code, PyDict globals, PyObject locals) in /Users/bruger/code/work/pythonnet/src/runtime/PythonEngine.cs:line 530\r\n   at Python.PythonTestsRunner.PythonTestRunner.RunPythonTest(String testFile, String testName) in /Users/bruger/code/work/pythonnet/src/python_tests_runner/PythonTestRunner.cs:line 64\r\n-----\r\n\r\nOne or more child tests had errors\r\n  Exception doesn't have a stacktrace\r\n```\r\n\r\n### Proposed Fix\r\n\r\nI understand that it is probably a bit complicated to actually override a virtual generic method in python code and maybe it is not even necesary. So maybe the best solution is to just ignore virtual methods in this case.\r\n\r\n\r\n","author":{"url":"https://github.com/rmadsen-ks","@type":"Person","name":"rmadsen-ks"},"datePublished":"2022-04-27T20:41:00.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/1776/pythonnet/issues/1776"}