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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Calling overridden method with out parameter from C# to python results in 0xC0000005 (Access Violation)","articleBody":"### Environment\r\n\r\n-   Pythonnet version: 2.5.2\r\n-   Python version: 3.8.3\r\n-   Operating System: Win10 64bit\r\n-   .NET Runtime: 4.8\r\n\r\n### Details\r\n\r\n-   Describe what you were trying to get done.\r\n\r\nIn C# I have defined an interface with a method with an out parameter. I implemented this interface in python, an now I want to call this method from C#. (using pythonnet)\r\n\r\nWhat I see is that a method without out parameter works fine, but a method with an out parameter throws an access violation.\r\n\r\nI know that out parameters are handled differently in pythonnet: you return a tuple with first the return value and the second tuple item is the out parameter.\r\n\r\n-   What commands did you run to trigger this issue? If you can provide a\r\n    [Minimal, Complete, and Verifiable example](http://stackoverflow.com/help/mcve)\r\n    this will help us understand the issue.\r\n\r\nMy C# code\r\n```C#\r\npublic interface IMyInterface\r\n{\r\n    string MyMethod_Out(string name, out int index);\r\n    string MyMethod(string name);\r\n}\r\n\r\npublic class MyServer\r\n{\r\n    public void CallMyMethod_Out(IMyInterface myInterface)\r\n    {\r\n        Console.WriteLine(\"C#.CallMyMethod_Out: before MyMethod_Out\");\r\n        int index = 1;\r\n        myInterface.MyMethod_Out(\"myclient\", out index);\r\n        Console.WriteLine($\"C#:CallMyMethod_Out: after MyMethod_Out: index:{index}\");\r\n    }\r\n    \r\n    public void CallMyMethod(IMyInterface myInterface)\r\n    {\r\n        Console.WriteLine(\"C#.CallMyMethod: before MyMethod\");\r\n        myInterface.MyMethod(\"myclient\");\r\n        Console.WriteLine($\"C#:CallMyMethod: after MyMethod\");\r\n    }\r\n\r\n    public void DoSomething()\r\n    {\r\n        Console.WriteLine(\"C#.DoSomething\");\r\n    }\r\n}\r\n```\r\n\r\nMy Python code:\r\n```python\r\nimport clr\r\nimport sys\r\n\r\nsys.path.append('some_dir')\r\nclr.AddReference(\"ClassLibrary1\")\r\n\r\nfrom ClassLibrary1 import IMyInterface, MyServer\r\n\r\nclass MyInterfaceImpl(IMyInterface):\r\n    __namespace__ = \"ClassLibrary1\"\r\n\r\n    def MyMethod_Out(self, name, index):\r\n        print(\"Python.MyInterfaceImpl.MyMethod_Out\")\r\n        other_index = 101\r\n        return ('MyName', other_index)\r\n\r\n    def MyMethod(self, name):\r\n        print(\"Python.MyInterfaceImpl.MyMethod\")\r\n        return 'MyName'\r\n\r\nprint('\\nCall regular C# function')\r\nmy_server = MyServer()\r\nmy_server.DoSomething()\r\n\r\nmy_interface_impl = MyInterfaceImpl()\r\n\r\nprint('\\nCall without out param')\r\nmy_server.CallMyMethod(my_interface_impl)\r\n\r\nprint('\\nCall with out param')\r\nmy_server.CallMyMethod_Out(my_interface_impl) # Access Violation 0xC0000005\r\n```\r\n\r\n-   If there was a crash, please include the traceback here.\r\n**Output:**\r\n\r\n\u003e Call regular C# function\r\n\u003e C#.DoSomething\r\n\u003e \r\n\u003e Call without out param\r\n\u003e C#.CallMyMethod: before MyMethod\r\n\u003e Python.MyInterfaceImpl.MyMethod\r\n\u003e C#:CallMyMethod: after MyMethod\r\n\u003e \r\n\u003e Call with out param\r\n\u003e C#.CallMyMethod_Out: before MyMethod_Out\r\n\u003e Process finished with exit code -1073741819 (0xC0000005)\r\n\r\n**Expected output**\r\n\u003e ...\r\n\u003e Call with out param\r\n\u003e C#.CallMyMethod_Out: before MyMethod_Out\r\n\u003e Python.MyInterfaceImpl.MyMethod_Out\r\n\u003e C#:CallMyMethod_Out: after MyMethod_Out: index:101\r\n","author":{"url":"https://github.com/roy-van-de-korput","@type":"Person","name":"roy-van-de-korput"},"datePublished":"2021-07-05T13:19:15.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/1481/pythonnet/issues/1481"}