Using Dynamic Proxies on Xamarin iOS

[ToddThomson]

I would like to be able to use Dynamic Proxies in a cross-platform .NetStandard 2 library I use for data access in Xamarin apps. I noticed that System.Reflection.Emit is referenced in Castle.Core which if used would cause grief on the iOS platforrm.

I simply want to create a dynamic proxy to intercept access requests to lazy load a data entity.

[jonorossi]

I noticed that System.Reflection.Emit is referenced in Castle.Core which if used would cause grief on the iOS platforrm.

I simply want to create a dynamic proxy to intercept access requests to lazy load a data entity.

@ToddThomson I recommend reading some of the DynamicProxy docs, you'll find the answers to why DynamicProxy uses reflection emit and why without it DynamicProxy is unable to work.

I've not used Xamarin iOS but you might be able to write something in your build that uses DynamicProxy to proxy a known set of types, then call ModuleScope.SaveAssembly (it defaults to CastleDynProxy2.dll but you can provide a name in the constructor), ship this assembly with your app, then call ModuleScope.LoadAssemblyIntoCache(Assembly) in the start up of your application. Doing this save/load dance means that DynamicProxy will have a set of generated/emitted classes in its cache to create proxy instances from.

This process was heavily used in the shared hosting days of medium-trust ASP.NET. We don't have a page in our docs with this, so if this works for you it would be great if you could put together a page.

I'll close this for now, if you run into problems with the save/load process feel free to log an issue.

[smartprogrammer93]

@jonorossi can you please provide a more detailed guide to your approach as it is the only solution to this problem.

[jonorossi]

@smartprogrammer93 Krzysztof has a blog post from a decade back with more detail and code snippets than I provided, the API still looks like the same.