How can I use AutoMapper with my Xamarin.iOS project?

Question

It seems that when I reference AutoMapper v3.1.0 in my Xamarin.iOS project, the build fails with this error message:

Error MT2002: Failed to resolve "System.Linq.Expressions.Expression System.Linq.Expressions.ExpressionVisitor::Visit(System.Linq.Expressions.Expression)" reference from "System.Core, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e" (MT2002)

When I roll back to the revision before I added this, it all works fine.

Unfortunately, I've already done quite a bit of work with AutoMapper in my unit tests and it would be problematic to remove it now. I guess that's a lesson to learn: just because it works in a test doesn't mean it works in Xamarin.iOS.

I would be very grateful if anyone has any ideas.

: I have now discovered a MonoTouch directory in the AutoMapper package, but referencing the AutoMapper.dll and AutoMapper.iOS.dll s found within does not solve the problem. ：我现在在AutoMapper包中发现了一个MonoTouch目录，但引用了AutoMapper.dll和AutoMapper.iOS.dll并没有解决问题。

: This issue only occurs when building for the device - I guess the MSIL to native converter doesn't like AutoMapper for some reason. ：此问题仅在为设备构建时发生 - 我猜MSIL到本机转换器由于某种原因不喜欢AutoMapper。 I'm trying to find a way to "hint" to this compiler that we need these symbols, which is what I think the purpose of the LinkerPleaseInclude.cs file is.

Answer 1

This issue is temporarily resolved - I had to hack out the offending symbols in AutoMapper and recompile it. Please see automapper issue #429 for more information on what symbols I removed. Until AutoMapper is updated to fix this problem, that's how you have to solve it for now.

The reason for this is explained concisely in another StackOverflow question - basically there are subtle differences between the .NET and Mono frameworks that in this case are incompatible with AutoMapper.

This answer previously stated that you should turn off linking to work with AutoMapper. While you can do this for development, it's not suitable for production use as it will yield a massive binary and you will not be able to submit your app to the app store.