How can I use non-Silverlight assemblies in a Silverlight app?

Question

I'm working an project (pure hobby, "Sharping my skills") which has one unified back-end and multiple front-ends (ASP.NET MVC 1.0/JQuery and Silverlight 2). When I try to add reference to my business layer assembly in the Silverlight 2 project (VS2008); It gets rejected, because it's not a Silverlight assembly.

Is their a way to include and reference a non-Silverlight assembly in a Silverlight app?

Answer 1

No there is not. Silverlight runs on a completely different CLR which is incompatible with the normal (desktop) CLR. It has an underlying different set of APIs in the BCL and most importantly a different metadata version number. These two factors, among others, prevent assemblies compiled for the desktop CLR from running by default on the Silverlight CLR.

All assemblies must be compiled specifically for silverlight.

Answer 2

Actually, whilst it is difficult and probably not a good idea, it is possible to reference CLR assemblies in a Silverlight project. David Betz has an example on his blog: http://www.netfxharmonics.com/2008/12/Reusing-NET-Assemblies-in-Silverlight

Again it's worth stressing that you probably don't really want to do this. The Silverlight framework has been developed by experienced engineers, who have put a lot of thought into what should be included and what shouldn't. Think about the CLR objects you think you need, and try to understand why they aren't currently available, and what the alternatives are.

Finally, remember that any CLR objects that you do add, will increase the size of your download.

Answer 3

No it't not possible to reference assemblies that are not built against the Silverlight runtime.

The way I have gotten around it is to create a new project for my business assemblies and then add all the classes from the original assembly to it. The key is that when you add them do it as an existing item and on the Add button click the down arrow and Add as Link. That way you still only have a single code base although you may have to add a few classes such as ApplicationException to make up for things missing from the Silverlight runtime.

Answer 4

The short answer is no, I'm afraid. The Silverlight runtime was designed to be a subset of the .NET framework, but the two are not directly compatible. (The runtimes are implemented quite differently, I believe, as Silverlight was designed to be cross-platform.)

The good news however is that you have a whole host of workarounds. This blog post and this CodeProject article discuss the issue in depth and offer a variety of clean solutions. Hope that helps...