Silverlight : CoreCLR and Revisiting Fundamentals

Silverlight is now in discussion everywhere since 3D support, Improvements in Controls and its availability on Mobile Devices announced informally by Bloggers across the world as everyone is awaiting for Silverlight 3. I still do find in community around me,many people just pulling out code from blogs/sites/forums without really bothering what’s happening under the hood. I already in my previous article, tried out my best to wipe out misconceptions about Silverlight, Now I am going few step ahead and discussing few Architectural things which I came across in last few days while working on Silverlight. My piece of research you can say.

Silverlight In Short…

Silverlight is technology introduced by Microsoft primarily with extensive usage of JavaScript to design and develop Rich Internet Applications which is also Cross Browser and Cross Platform, further after certain period of time, Microsoft introduce Silverlight programming with Managed environment with coding languages like C# and then they went one more step ahead and made capable people to program Silverlight with IronRuby with making use of DLR [ Dynamic Language Runtime].

Something worth to know about CoreCLR…

Microsoft done enormous efforts to design Silverlight Architecture, I can say best ever I have seen. Real challenge was to keep CLR size minimum which is required to execute Silverlight Applications. Imagine what if Silverlight was dependent on Desktop CLR?, was not a good solution, so Microsoft introduced a compact or subset of Desktop CLR which we call now as “CoreCLR”, which plays a vital role in overall Silverlight application execution and can be download easily even on small bandwidth.

How it differs CoreCLR and Desktop CLR ?

Sometime its like puzzle, we have template of Silverlight in Visual Studio, we use C#, then why there is nothing called like scsc.exe etc., Well Visual Studio while compiling Silverlight application uses the same C# compiler which is getting use to develop full fledge C# based application, If you observe carefully on .NET command prompt by typing csc/? , you will find an attribute as “/nostdlib[+|-]”,yes, Visual Studio make use of same argument “nostdlib” to instruct Compiler to not to use the libraries of Desktop CLR and to refer Core CLR, like it is written in the description of nostdlib attribute “Do not reference standard library (mscorlib.dll)”.

This is how CoreCLR comes into picture, so we can say that if someone want to develop or Run Silverlight application, then he/she can move ahead without having Desktop CLR, If someone have Desktop CLR, in that case both CLRs will be parallel to each other.

What’s inside CoreCLR ?

I said in above para that, it is subset of Desktop CLR, that doesn’t mean CoreCLR will give each and every features of main CLR, Those Libraries are re-written for Silverlight so as to make CoreCLR size as compact as possible, so you may not find namespaces like System.Data or some generic collections like ArrayList etc., So to overcome these and give developers all facilities so that he/she can relate with ASP.NET and use full features for Data driven and other applications, Service model was put ahead to address these kind of issues, so now like ASP.NET, you can maintain session,implement caching, Bind controls with data and do all CRUD operations with Grid using Web Services, You can do this with ASMX services,WCF or Silverlight enabled WCF services.

Coming back to fundamental again, like main CLR, in CoreCLR you have JIT, BCL and CLR Execution Engine, Yes you have all those basic dlls which you need to program Silverlight are now available including mscorlib.dll at location :

C:\Program Files\Microsoft Silverlight\2.0.31005.0

A question may arise, how I get this CoreCLR on my machine, you remember when you don’t have Silverlight then you download a small plugin, Well..this is it, Runtime for Silverlight.

Web Browser makes it happen…

We all feel that our IE/Mozilla or any other, just render the pages and their duty is over, Well for Silverlight, Browsers have vital role to play.Once you request ASP.NET or HTML page which hosts Silverlight, Browser makes a GET request for initial XAP and Silverlight Runtime Control downloads it. ( I recommending you to read more on “WebClient”, will make sense). Browser hosts Silverlight using our traditional mechanism of ActiveX. What is then exact role of agcore,coreclr,npctrl.dll files?

What is the role of npctrl.dll ?

When Browser host Silverlight using ActiveX mechanism. npctrl.dll which is nothing but Browser Plug-in co-ordinates with agcore.dll file [ Hope you all remember agcore.dll is with us from first version of Silverlight, when there was no concept of CoreCLR ], agcore.dll then coreclr.dll [ CoreCLR just for your awareness, is combination of Managed Code + Unmanaged Code ], so now CoreCLR does all management work for Silverlight application like memory management and other resources usage, since the native code of CoreCLR is capable of talking directly with Operating System, This is how due to its existence in Browser process, CoreCLR and Desktop CLR can go parallel to each other.

What if Browser process goes down??

By closing Browser process or getting it shutdown accidently will release all resources hold by CoreCLR, In overall process, one thing may come to your mind, what happens to XAML then?, Like we all know for WPF, XAML is converted into appropriate BAML for better understanding by Browser. 

Something more to talk…

Silverlight defined as Cross browser and Cross platform, above few lines says CoreCLR is combination of Managed and Unmanaged Code, so how then it works on Linux and Mac platforms?, Well as far as Linux environment is concern, you have some fundamental framework as Project Mono with Silverlight’s implementation as Moonlight. For Mac, you have a component in CoreCLR known as PAL [Platform Adaptation Layer] which is responsible to communicate between Mac and Silverlight.

What is possible in Silverlight?

Like ASP.NET, Database Connectivity and Operations, Session Management, Caching, Socket Programming, Streaming of Media and Images,Usage of Generics up to some level, ADO.NET/Entity Framework incorporation etc. now possible with usage of Web Services.

Few unanswered questions…

Is Silverlight Secure? especially if someone dissects the XAP to ZIP and reuse some unique logic? Is Code obfuscation with tools will really make it secure?,since XAP exposes some resources and even Service configuration files. Will Silverlight run on Mobile Devices with same CoreCLR? or the CoreCLR for mobile devices will be subset of Compact Framework?..Interesting to know in coming future..

On ending note..

My this article is motivation given to me by one MSDN Magazine article, Hope my this little effort will help you to have better in-depth vision on Silverlight & CoreCLR. Intention of re-writing all the stuff again and derive it from various sources available on net is to make all people comfortable on Silverlight and not to just blindly compare it with Flash.

All information I am sharing here is part of my research and references taken from MSDN Magzine article, might not be accurate in some area but I did tried out my best to make it exact and to the point and specific with the topic.Let me know your feedback and suggestions on this.

Vikram.