Skip to main content

Fun with Dynamic Objects and MEF in C# 4.0





About .NET 4.0 Series - I'll be covering various aspects of .NET 4.0 and related technologies in these posts

C# 4.0 introduced the dynamic keyword, to support dynamic typing. If you assign an object to a dynamic type variable (like dynamic myvar=new MyObj() ), all method calls, property invocations and operator invocations on myvar will be delayed till the run time, and the compiler won't perform any type checks for myvar at compile time.

So, if you do something like myvar.SomethingInvalid(); it is valid at compile time, but invalid at runtime if the object you assigned to myvar doesn't have a SomethingInvalid() method.
The System.Dynamic namespace has various classes for supporting dynamic programming, mainly the DynamicObject class from which you can derive your own classes to do run time dispatching yourself.

A couple of points to note.
  • A dynamic call will be slower for the first time, and your calls will be jited and cached if possible for subsequent calls. As a first step, the DLR checks the cache to see if the given action has already been bound wrt to the arguments. If not, the DLR checks to see if the receiver is an IDynamicObject, and if so, asks the receiver to bind the action. If the receiver is not an IDO, then DLR calls into the language binder (i.e, the C# runtime binder), and cache this.
  • C#'s underlying type system has not changed in 4.0. As long as you are not using dynamic keyword, you are still statically typed (i.e, the types are known for the compiler at compile time).
  • Error handling when you use dynamic features is a bit difficult and can't be very specific, as you don't know much about the foreign objects to which you dispatch the calls.
Recently, I published this article in Codeproject; 
This article demonstrates a couple of interesting techniques, including.
  • Creating a dynamic wrapper around the file system so that we can access Files and Directories as properties/members of a dynamic object
  • A way to attach custom Methods and operators to our dynamic wrapper class and dispatch them to a plug in sub system.

Comments

Popular posts from this blog

Top 7 Coding Standards & Guideline Documents For C#/.NET Developers

Some time back, I collated a list of 7 Must Read, Free EBooks for .NET Developers, and a lot of people found it useful. So, I thought about putting together a list of Coding Standard guidelines/checklists for .NET /C# developers as well.As you may already know, it is easy to come up with a document - the key is in implementing these standards in your organization, through methods like internal trainings, Peer Reviews, Check in policies, Automated code review tools etc. You can have a look at FxCop and/or StyleCop for automating the review process to some extent, and can customize the rules based on your requirements.Anyway, here is a list of some good Coding Standard Documents. They are useful not just from a review perspective - going through these documents can definitely help you and me to iron out few hidden glitches we might have in the programming portion of our brain. So, here we go, the listing is not in any specific order.1 – IDesign C# Coding StandardsIDesign C# coding stand…

5 Awesome Learning Resources For Programmers (To help you and your kids to grow the geek neurons)

Happy New Year, this is my first post in 2012. I’ll be sharing few awesome learning resources I’ve bookmarked, and will be pointing out some specific computer/programming related courses I've found interesting from these resources.Also, thought about saving this blog post for my kids as well - instead of investing in these Child education schemes (though they are too small as of today, 2 years and 60 days respectively ). Anyway, personally my new year resolution is to see as much videos from this course collections (assuming I can find some free time in between my regular job && changing my babies diapers).1 – Khan AcademyAs I mentioned some time back, you and your kids are missing some thing huge if you havn’t heard about Khan Academy.  It is an awesome learning resource, especially if you want to re-visit your basics in Math, Science etc.With a library of over 2,600 videos covering everything from arithmetic to physics, finance, and history and 268 practice exercises, th…

Hack Raspberry Pi – How To Build Apps In C#, WinForms and ASP.NET Using Mono In Pi

Recently I was doing a bit of R&D related to finding a viable, low cost platform for client nodes. Obviously, I came across Raspberry Pi, and found the same extremely interesting. Now, the missing piece of the puzzle was how to get going using C# and .NET in the Pi. C# is a great language, and there are a lot of C# developers out there in the wild who are interested in the Pi.In this article, I’ll just document my findings so far, and will explain how develop using C# leveraging Mono in a Raspberry Pi. Also, we’ll see how to write few minimal Windows Forms & ASP.NET applications in the Pie as well.Step 1: What is Raspberry Pi?Raspberry Pi is an ARM/Linux box for just ~ $30. It was introduced with a vision to teach basic computer science in schools. How ever, it got a lot of attention from hackers all around the world, as it is an awesome low cost platform to hack and experiment cool ideas as Pi is almost a full fledged computer.  More About R-Pi From Wikipedia.The Raspberry Pi