Assembly error after upgrade (9 to 10)

If it is a WebApp project have you rebuilt it so it references the new Version 10 libraries?

Have you made absolutely sure that there are no v9 DLLs left in the bin folder? Sometimes legacy files do hang around following an upgrade (add the product version column in windows explorer to check). You want to make sure that any DLLs in the format CMS.XXX which are version 9 have been deleted.

@Suneel Jhangiani - The project builds fine in Visual Studio but unfortunately still the same result

@Peter Cranston - I have checked through the project and all of the DLLs have been updated to version 10 (including the one which causes the error)

Just to be clear, it is not CMS.Core that is causing the error, it is another version 9 DLL that is referencing CMS.Core version 9 but cannot find it such as CMS.CKEditor.dll or CMS.ControlsXmlSerializers.dll. These are both DLLs that are no longer used in kentico 10 and should be removed by the upgrade but in some cases are not.

@Peter Cranston - Ahhhh that makes sense the CMS.ControlsXmlSerializers.dll is still in there and on version 9.0.0.0! Do I have to remove it from the /Lib folder as well as the /bin folder?

Yes, remove any occurrence or reference to it in the project.

@Peter Cranston - Unfortunately removing the files from both the /Lib and /bin files stil gives the same error, would they be located anywhere else in the project perhaps?

Check the CMSDependencies folder

You could also try mapping the older version calls to the newer version and see if that helps you find the offending assembly - add the following to the configuration element in your web.config:

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
        <dependentAssembly>
            <assemblyIdentity name="CMS.Core" culture="neutral" publicKeyToken="834b12a258f213f9" />
            <bindingRedirect oldVersion="0.0.0.0-9.0.0.0" newVersion="10.0.0.0" />
        </dependentAssembly>
    </assemblyBinding>
</runtime>