.NET Portable Class Library [Serializable] Attribute

Question

I have a common class library containing many models for my server and my client. Since the client is running under Xamarin, the common library must be a Portable Class Library (PCL).

In my server, these objects are passed around with AppDomain Remoting/Marshaling, so to my understanding an object either needs to be marked as [Serializable] or inherit from MarshalByRefObject

Being in a PCL, I cannot do either of these things to any of my models.

My question is: How can I make these objects work with AppDomain Remoting/Marshaling and let them reside in a Portable Class Library?

Answer 1

I have created a PCL support library called CSShim that contains a "mock" [Serializable] attribute. If this library is referenced from your PCL library, you can use [Serializable] in your code.

Then, when you consume your PCL library in a regular .NET desktop application, the reference to the PCL CSShim is replaced with a reference to the .NET anolugue of CSShim, using the so-called "bait-and-switch" technique. The .NET analogue forwards the invocation of [Serializable] to the .NET implementation in mscorlib using [TypeForwardedTo].

CSShim is currently available from NuGet for PCL profile 259, targeting .NET Framework 4.5 and higher, Windows 8 and higher, Windows Phone 8.1, Windows Phone Silverlight 8 and higher, Xamarin Android and Xamarin iOS.

The CSShim source code is available on Github. If it is a limitation that the PCL library only targets .NET 4.5 and higher, you could theoretically re-target the PCL library to a .NET Framework 4 profile such as profile 328, although re-targeting may be "a rough ride" :-)

Alternatively, you could create your own PCL support library containing only "mock" implementations of the types related to SerializableAttribute, and create a .NET analogue of the support library using type forwarding to invoke the valid types in the .NET core assemblies. I have outlined this approach in more detail in this StackOverflow answer.