https://community.graphisoft.com/t5/Archicad-C-API/ACAPI-CallUndoableCommand-Access-violation-reading-location/m-p/279331#M2609 <DIV class="actalk-migrated-content">Hi.<BR />I call ACAPI_Property_CreatePropertyDefinition api, and the return code is NoError.<BR />But I don't why the access violation occurs.<BR /><BR />I call ACAPI_Property_CreatePropertyDefinition in the callback of APINotify_Open event.<BR /><BR />Archicad version 22.<BR />VS 2015</DIV> Thu, 29 Sep 2022 07:47:20 GMT Anonymous 2022-09-29T07:47:20Z https://community.graphisoft.com/t5/Archicad-C-API/ACAPI-CallUndoableCommand-Access-violation-reading-location/m-p/279331#M2609 <DIV class="actalk-migrated-content">Hi.<BR />I call ACAPI_Property_CreatePropertyDefinition api, and the return code is NoError.<BR />But I don't why the access violation occurs.<BR /><BR />I call ACAPI_Property_CreatePropertyDefinition in the callback of APINotify_Open event.<BR /><BR />Archicad version 22.<BR />VS 2015</DIV> Thu, 29 Sep 2022 07:47:20 GMT https://community.graphisoft.com/t5/Archicad-C-API/ACAPI-CallUndoableCommand-Access-violation-reading-location/m-p/279331#M2609 Anonymous 2022-09-29T07:47:20Z https://community.graphisoft.com/t5/Archicad-C-API/ACAPI-CallUndoableCommand-Access-violation-reading-location/m-p/279332#M2610 I'm pretty sure you can't process undoable actions during the callback for a project event notification. The right approach would be to ask ARCHICAD to notify you when it's appropriate to action this process – I suggest that you take a look at <I></I><S><I><I></I></I></S>ACAPI_Command_CallFromEventLoop<E></E> Fri, 13 Dec 2019 10:39:02 GMT https://community.graphisoft.com/t5/Archicad-C-API/ACAPI-CallUndoableCommand-Access-violation-reading-location/m-p/279332#M2610 Ralph Wessel 2019-12-13T10:39:02Z