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POTable-per-hierarchy and inheritance implementation issue
 

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  1. POTable-per-hierarchy and inheritance implementation issue
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    <p>I am migrating an old ASP application to a modern .NET version, to cut down on development times we are looking at the .NET 4.0 Entity Framework. However, we seem to have hit a brick wall in our development with this issue.</p> <p>Given is a small part of our database: A table OBJECT which contains a list of cars and their respective properties. We also have a table OBJECT_OPTIONS which contains, for a given car in OBJECT, a list of OPTIONS, ACCESSORIES and STANDARD EQUIPMENT. These three types all have the same fields and are therefor stored in the same table. The column ncopt_type is used to discriminate between the different lists. Possible values are: 'opt', 'acc' and 'sta'. The table OBJECT_OPTIONS links to OBJECT via ncopt_obj_id which represents a unique car (obj_id) in table OBJECT.</p> <p>Our goal is to provide the OBJECT entity with 3 properties that link to the different OBJECT_OPTIONS lists: - property OPTIONS - property ACCESSORIES - property STANDARDEQUIPMENT</p> <p>We've tried different tutorials and walkthroughs concerning the table-per-hierarchy via inheritance model but haven't succeeded in creating a buildable model.</p> <p>Technically what we did was:</p> <ul> <li>Create entity OBJECT</li> <li>Create entity OBJECT_OPTIONS, make it abstract</li> <li>Add entities OPTION, ACCESSORY and STANDARD_EQUIP all using basetype OBJECT_OPTIONS</li> <li>Add conditions to all three tables on ncopt_type = '...'</li> <li>Add 3 navigational properties to OBJECT, all linking to one of the inherited entities: OPTIONS, ACCESSORIES and STANDAARD_EQUIPMENT</li> </ul> <p>A bunch of errors shows up during this setup, but we end up with this one: </p> <blockquote> <p>Error 3032: Problem in mapping fragments starting at lines 250, 286:EntityTypes NCO.Model.OPTION, NCO.Model.ACCESSOIRE, NCO.Model.STANDAARD_EQUIP are being mapped to the same rows in table OBJECT_OPTIES. Mapping conditions can be used to distinguish the rows that these types are mapped to.</p> </blockquote> <p>There is a condition present on all three objects though.</p> <p>I have found no solution to this problem and have spent way too much time on it already. We are currently using a workaround method but would love to get this fixed as this situation will present itself a few more times by the end of the project.</p> <p>Any help appreciated, if you need more information, please drop me a comment or an email.</p>
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    1. USBram Vandenbussche
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      1. USAntoine Aubry
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    1. COSo, ehm, no one knows?
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      1. USBram Vandenbussche
    2. COIt would appear not. I've got the same problem,...maybe it's just us two!
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      1. USStimul8d
    3. COCould you attach an image of the relevant tables and of the relevant entities from the edmx? - It would help clarify what you are trying to do. Leave a comment here after editing.
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      1. USDanny Varod
 

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