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iosxamarinlinkerautofac

Autofac Build() throws exception on latest Xamarin iOS when Linker configured to Link All

After upgrading to Visual Studio 16.3.0 (Visual Studio for Mac 8.3.1805) Autofac throwns an exeception when doing builder.Build() in a project that previously worked:

The type 'Autofac.Features.Indexed.KeyedServiceIndex'2' does not implement the interface 'Autofac.Features.Indexed.IIndex'2'

With this release of Visual Studio (and maybe earlier versions too), iOS is compiled using Mono 6.4.0.198 and I suspected that this might be what is introducing the braking change. Alternatively the linker behaves differently with the latest tool-chain. All I can say is that this used to work and now it doesn't.

Following these guidelines is not sufficient: Cross-Platform and Native Applications

Solution

  • To work around the issue, first make sure that Autofac is installed both in the iOS project, Android and the .NET Standard shared project, then choose one of these two options:

    1. Set the linker to Don't link or Link Framework SDK's Only
    2. Or, you can; add --linkskip=Autofac (case sensitive!) to the Additional mtouch arguments in iOS Build found in the iOS project properties.
    3. Or, you can; create a Custom Linker Configuration file, which I btw think is the best option if you need linking. It's a little bit more work, but when using a Linker Description file the compiler will give you usable feedback when you build, if you've made a mistake like misspelling an assembly etc. Also, the Linker Description file has an identical format across Android and iOS.

    Note: Option 2 and 3 will only increase your app size a small amount, as it will ensure that all of the Autofac assembly is included in your app package, while all other assemblies not specified as part of 2 or 3 will continue to be linked.

    I assume that the needs for one of these work-arounds is an indication that Autofac is currently not linker safe.