+35  Q: 

Silverlight vs Flex

My company develops several types of applications. A lot of our business comes from doing multimedia-type apps, typically done in Flash. However, now that side of the house is starting to migrate towards doing Flex development.

Most of our other development is done using .NET. I'm trying to make a push towards doing Silverlight development instead, since it would take better advantage of the .NET developers on staff. I prefer the Silverlight platform over the Flex platform for the simple fact that Silverlight is all .NET code. We have more .NET developers on staff than Flash/Flex developers, and most of our Flash/Flex developers are graphic artists (not real programmers). Only reason they push towards Flex right now is because it seems like the logical step from Flash.

I've done development using both, and I honestly believe Silverlight is easier to work with. But I'm trying to convince people who are only Flash developers.

So here's my question: If I'm going to go into a meeting to praise Silverlight, why would a company want to go with Silverlight instead of Flex? Other than the obvious "not everyone has Silverlight", what are the pros and cons for each?

+10  A: 

The problem with Silverlight, is that there's still a lot of people who don't have it installed. Also, I"m not sure how well your existing .Net developers will be able to leverage their existing skills if they are only familiar with more traditional server-side .Net coding.

What are your reasons for pushing Silverlight over Flex? If you have to ask the SOFlow community for reasons, it seems odd that you would be so willing to push it.

Just wait for MS to push it onto the automatic updates and 99% penetration will be achieved.
Andrei Rinea
Yes, of course. Exactly the same way 99% of IE users use IE7, and no one uses IE6, because IE7 was pushed through automatic updates. Yes.
Unfortunately it still seems that about 30% of IE users are still using IE6...
The silverlight install is pretty easy for users that don't have it.
I agree with Craig. Easier than Flash to install.
You're forgetting Flash comes bundled with most browsers already.
My recent install of FF3 required me to install Flash separately. And the Silverlight install was easier.
Notice that when most users buy a computer, it already as Flash installed. And unfortunately Andrei Rinea as a point, when Microsoft wants the users to install something they just put it on the Recommended updates catalog....
Fábio Antunes
In point of fact, Flash does not come bundled with IE, FF or Chrome.
Christian Nunciato
IE6 users exist? *brain explodes*
@Christian - Update to this, Flash is now bundled in chrome in chrome in the dev channel.
Nick Craver


I edited my post to try to elaborate more.

+1  A: 

I think Silverlight and XAML is preferable to ActionScript, and though I'm not familiar with ActionScript IDE's, I am familiar with VS2008 and Expression Web/Blend, and they are very good development environments and getting better all the time. I would go with Silverlight, and I think the key to getting users to install the plug-in is to have a good plug-in detect page that explains what SL is and why they need it. For an example of this, go to and try it with your SL plug-in disabled.

+3  A: 

As Kibbee hinted at above, the argument of leveraging existing .Net developers doesn't hold much water. It is impossible to be an expert in all facets of .Net development. The platform is just too big. The same goes for Java. The only thing Silverlight has going for it from a skills perspective is that you can code in your favorite .Net language. That advantage is fairly small if you are already doing any significant web development that utilizes JavaScript since Action script is a variation. So really to convert a programmer to either Flex or Silverlight is all about learning the platform's API.

Sam Corder
+14  A: 

I think Silverlight is most advantageous for companies that have .NET developers but noone with designer experience.

Skill sets will be easier to find as far as finding C# or VB developers vs finding ActionScript guru's. However there is the trade off:

Design experience is an investment not only in Designers with artistic skill, but also in the knowledge and tools provided by Adobe. You can nearly guarantee that a professional designer uses a mac and has experience with Adobe tools.

Right now the Silverlight designer tools are half baked and can be a headache. For instance Blend errors when trying to render any xaml containing an IValueConverter, this is problematic. I have no idea what the Adobe developer experience is, I'm sure it is as hairy.

So at this stage of the game it comes down to human resources:

If you have .NET experience and little invested in Design skills go Silverlight. Programming skills/tools will be transferable. If you have Design experience and skill set go with Flex. Designer skills/tools will be transferable.

Either way both client platforms require communication with services to get data, so you will always leverage your existing programing expertise on the back end.

Paraphrased Jon's opinion from a different point of view:

I think you should look at Flex as a long-term play, just as Adobe seems to be doing. There's an obvious balance on when to use Silverlight vs. Flex when you're concerned about reach and install base, but here are more reasons Flex is a good direction to move in:

  1. Second mover advantage - Just as Adobe built a "better Java Applet" with Flash, they're able to look at how you'd design a runtime from scratch, today. They have the advantage of knowing how people use the web today, something the inventors of existing client platforms could never have accurately guessed. .NET can add features, but they can't realistically chuck the platform and start over.

  2. Designer familiarity - While Flex/AIR is a new programing model, it's not entirely unfamiliar to designers. They'll "get" the way Flex works a lot more quickly than they'll understand firing up a new design environment with new feature poor tools and new animation paradigms.

  3. Being rid of the RGB color model in Silverlight- .NET was originally built for windows and it is at the core of how it works. Flex ditched a long time ago for an design-centric model.

  4. All your tools run on your mac. Nuff said.

  5. Cool features - Silverlight still has some catching up to do with Flash on some obvious features (like webcam / mic integration, or 3d / graphics acceleration).

Brian Leahy
Go watch the videos of QuakeLight and tell me that Silverlight has some catching up to do in graphics. Also: "All your tools run on your mac. Nuff said." Apparently macs are perfect.
In my experience, developers can pick up new programming languages faster than designers can pick up new design software. They're even more stuck in their ways than us!
@jcollum: actually quake was also ported to flash ( using Alchemy (
what does 'design skills' have to do with writing a proper flex application? It is more than capable of making stock apps that looked like a developer 'designed' them.
Joel Hooks
"You can nearly guarantee that a professional designer uses a mac and has experience with Adobe tools."If you've used Flex Builder at all, you'd know that "previous experience with Adobe tools" is not a benefit. It's built on top of Eclipse, and will be foreign to anyone without previous programming IDE familiarity.
+36  A: 

I think you should look at Silverlight as a long-term play, just as Microsoft seems to be doing. There's an obvious balance on when to use Silverlight vs. Flash when you're concerned about reach and install base, but here are some reasons Silverlight is a good direction to move in:

  1. Second mover advantage - Just as Microsoft built a "better Java" with .NET, they're able to look at how you'd design a RIA plugin from scratch, today. They have the advantage of knowing how people use the web today, something the inventors of Flash could never have accurately guessed. Flash can add features, but they can't realistically chuck the platform and start over.

  2. Developer familiarity - While Silverlight is a new model, it's not entirely unfamiliar to developers. They'll "get" the way Silverlight works a lot more quickly than they'll understand firing up a new development environment with a new scripting language and new event paradigms.

  3. Being rid of the timeline model in Flash - Flash was originally built for keyframe based animations, and while there are ways to abstract this away, it's at the core of how Flash works. Silverlight ditches that for an application-centric model.

  4. ScottGu - ScottGu is fired up about Silverlight. Nuff said.

  5. Cool new features - While Silverlight still has some catching up to do with Flash on some obvious features (like webcam / mic integration, or 3d / graphics acceleration), there are some slick new technologies built in to Silverlight - Deep Zoom is one example. I'm seeing more "revolutionary" technologies on the Silverlight side, while Flash seems to be in maintenance mode at this point.

Jon Galloway
If you work just in Flex, you as well might have no clue that there ever was any timeline at all. That is a non-issue.
Check this
1. a better Java, just not a cross-platform (mono rocks though) Adobe did chuck the player away and start again with AVM2 and AS32. agree3. Timeline is optional now (use sprite instead of movieclip)5. Flash absolutely does NOT have 3D acceleration, so that's a tie. deep zoom is cool but pointless
Actually, Jon, in all due respect, you're comparing Silverlight to Flash, not Flex, which is a typical point of confusion by Silverlight proponents. I've written an enterprise-level application in Flex (which compiled to SWF), but wouldn't even know where to begin to write a Flash app.
Flash is very different than Flex, (and actually there is a framerate and those things inn Flex too but they are not used and its a bad practice) Flex is also much faster than Flash, I would suggest you take a look at the C++ interpreter built with Flex. Silverlight player is not available that much
@analytik. He was talking about Flash, not Flex to be fair :) Silverlight in Framework mode also doesn't have time associated to it, so its really apples/oranges :)@troylar I've written Enterprise solutions in Flex/Flash for many years, its doable and similar architectural principles apply. Flex obviously has a reduced amount of friction associated to it. Its early versions did have dependencies on Frames but since the latest addition to the AVM++ Sprite vs MovieClip [email protected] Silverlight is on 1 in 3 machines - 400million installs (more people have SL than iPhones,iPods,Twitter etc).
Scott Barnes
Yeah, but if kevgriff goes into a meeting and says Scott Guthrie praises Silverlight, his coworkers are gonna say "Who?".
Jon Galloway works for Microsoft. Nuff said.
@ilk - I started working at Microsoft in December 2009. I posted this answer in August 2008. I took a job at Microsoft because I like their developer products, not the reverse. Nuff said.
Jon Galloway
+17  A: 

There's two questions here: Silverlight vs. Flash as platform and Silverlight vs. Flex as RIA framework.

The first question depends on your timeframe. Flash Player has over 95% reach, Silverlight has no way near that. However, Silverlight may get there, it is after all backed by Microsoft. If you aim to launch a site next week and want a huge audience, Silverlight is not an option. If you aim to launch a really cool application that everyone would want to use it's a bit different, if your app is good enough your target audience may install Silverlight just to be able to run it.

As for the second question its a matter of how easy it is to develop applications in Silverlight. Flex isn't just a set of widgets, it's a very big framework that does a lot of thing that ease the work of the developer. You could write the same applications using only the core Flash API, but it would be very much more work. Depending on what's available in Silverlight, this should be an important factor when deciding. If you can cut development time, is having two platforms worth it?

+3  A: 

Silverlight programmer's don't know what they're missing out on, when it comes to Flex. Silverlight lacks the component model and event triggering capabilites that Flex has. Using XNA, and C#, a friend of mine has to jump through all kinds of hoops to get his Silverlight application to work. Then, it has to be handed off to a designer to get it to look half way decent.

Listen to the podcasts on Silverlight, and you'll hear how even a couple guys that really push Silverlight, acknowledge some of these issues. (I think, if I recall correctly, one of the guys works for Microsoft, but I could be wrong - I listened to it last week). They agree that Silverlight isn't quite ready for any huge applications, in its current state.

I would go with Flex, for a nice clean, straightforward approach - especially if you're already familiar with Flash and ActionScript 3.0. Flex makes alot more sense, in my opinion - Silverlight still has to mature.

-1. What does XNA have to do with Silverlight? They aren't directly connected like you imply. And 99% of programmers really *should* hand their stuff off to a designer long before releasing it to the public :)
+8  A: 

Another advantage of Flex development is that you can switch to developing desktop applications (Adobe AIR) with the same source code (and same IDE) and distribute them from web. Seriously, check out for the future of Flash platform.

Also, Flash Player 10 includes 3D with hardware acceleration. How amazing can you get with 3MB runtime environment?

Also, Flash Player 10 includes 3D with hardware acceleration - SADLY NOT!
What are you babbling about?
Agreed on AIR (may be very important), but no 3d support (yet).
We most also notice that Air was release in the early 2008, its very young, of course that with time it will get even better. I can't give a "no side opinion" because i just don't like Microsoft Business/Marketing methods. But if it wasn't for then we wouldn't be in the current state of technology as we are.
Fábio Antunes
Flex has Air, Silverlight has WPF. I don't think there's enough difference for this to be an argument one way or the other.
Silverlight 3 comes with the "out of browser" feature where your silverlight app can be installed to the desktop just like an AIR app. There are APIs for detecting when the app is running in the browser or not, when there is an internet connection present, and even an API for updating the app automatically.
Jason Miesionczek
+4  A: 

Asa graphics designer, I've used Flash (on and off) over the last few years, and Silverlight (and its big brother WPF) over the last 1.5 years. Based on what I've heard from my team (all of whom are developers or former developers, if your .Net developers will be doing all the programming, go with Silverlight. I love Flash, but even with the OOP overhaul to ActionScript 3 in Flash 9 and up, it's still a somewhat quirky language, and going back and forth between AS3 and C# will probably drive your developers nuts :-).

For your designers, do the following:

  • Get them a copy of Expression Blend, the GUI development tool for Silverlight/WPF.

  • Blend has a somewhat steep initial learning curve, and the interface throws a ton of variables/options at you, so invest in some training, and give your designers time to get up to speed with the UI.

  • Speaking of training, get a subscription to the video library, esp. the Lee Brimelow Expression Blend training course.

  • Caveat emptor: Blend and WPF change rapidly, so sometimes you'll run into bugs in Blend that are fixed in the next beta/CTP of Blend. E.g. There was a bug in Blend 2 that prevent my storyboards (animations) from working in a recent project. I upgraded to Blend 2.5CTP, and it worked.

  • Silverlight content doesn't always seem to work with the latest Beta of the Silverlight plugin, just something to keep in mind if you're testing some new feature that's only available in the latest Silverlight plugin.

  • Invest in a powerful system (Quad Core, 4Gigs of RAM, etc.) Blend consumes a lot of resources, esp. when you have tons of layers. E.g. I'm working on an app with over a 100 layers(!) in the base app (and another 100+ in some of the user controls), and about 40-50 storyboards. Every few minutes, I have to restart Blend, because the UI stops responding (but doesn't freeze). Either that, or move everything you can into user controls.

The Loud Ninja
"100 layers(!) in the base app (and another 100+ in some of the user controls), and about 40-50 storyboards": man it sounds like you need to work on breaking things out into more user controls. Surely you aren't working on all of those things within the same few minutes?
+5  A: 

Not to forget:

Flex is very much cross platform, as it is compiled using as Java compile which means that you can easily use Mac or Linux when developing Flex applications. I've my current cruisecontrol setup (which uses Linux) I build build Flex applications, but the development guys uses both Mac, Linux and Windows.

In my experience, java developers feels quite at home in Flex Builder since it is based on Eclipse.

Martin Wickman
I have to say C# developers feel good about Flex too, since the chief designer for Flex was in .Net team originally
And you can also use Eclipse with the Flex Development plugin which does the same as Adobe Flex.
Fábio Antunes
+6  A: 

You will never get an fair vote to this question on SO as it has so many Microsoft devs.

Also, people will probably down vote this answer, which says it all really.

I say let your developers try both platforms, and see which they prefer.

To answer the comments below, I just noticed that while there are lots of answers recommending Flash / Flex, the ones for Silverlight have many more up votes. It's not a matter of lying, it's just favouring what you're familiar with, not necessarily the best platform.

I see more people favoring Flex than Silverlight, SO might be more dominated by .Net people but its certainly not biased
So Microsoft devs are automatically not honest? Is everyone who disagrees with you a liar?
Joel Mueller
+1  A: 

We went through this same issue and Flex won hands down. Our .NET developers were concerned at first, but after working so long in the pain of Ajax and JavaScript, they now LOVE and really enjoy working in Flex.

Here's a simple test for you . . . try to find at least 3 examples of real-world Silverlight applications (that aren't games, video players or gadgets). Then do the same for Flex.

"the pain of Ajax and JavaScript" <-- has nothing to do with the current implementation of Silverlight, it uses no JS
+1  A: 

I use this rule of thumb: if your company is developing internet based multimedia software, and has customers with all sorts of platforms, and you are not doing database intensive applications Flex is the definite answer, if your company develops both internet and DVD based products, less interactive but more intensive (CPU, Memory) and uses ridiculous amount of database transaction Silverlight makes more sense

+2  A: 

Someone said: "Find 3 real world silverlight applications". Ok, I knew some off the top of my head but I googled it anyway. The list:

  • 2008 Beijing Olympics (stats here, 250TB of data delivered!)
  • Netflix on-demand player
  • AOL email client (may not be released yet)

Oh, not video players? Well that leaves the UFC application (it's a hybrid video/chat/other stuff) and the AOL email client. Silverlight excels at video and that's where it's gaining it's foothold but that doesn't mean it can't do other things. I see no reason to dismiss it just because it does video well.

Infoworld [link] said that "Silverlight has substantial technical merit and relatively good performance. It's a very capable RIA technology that's especially useful in the hands of programmers with .Net experience and designers with XAML experience." It's a good article for you to read regarding your question.

My answer: if you have a team of devs that are comfortable with .NET then Silverlight should be first on your list. If not, then it's a real tossup. I've seen articles say that Visual Studio is a superior development platform compared to what you use with Flex. But Flash is damn near ubiquitous.

Also keep in mind that Silverlight 2 uses almost no Javascript (I think none, but I'm not positive). So any avoidance of Silverlight because of JS is unfounded.

If performance matters, Silverlight wins there. I've seen my browser's CPU usage go to 100% many times and killing whatever window is running Flash always got rid of it. It's especially obvious in Chrome where you can see the process that's consuming your CPU. If your interested in Silverlight for gaming potential, look for QuakeLight, the Silverlight port of Quake. It's shaping up really well.

I really think it comes down to where your developer talent lies and what kind of application you'll be delivering. Simple game? Flash. Line of business app? Silverlight. In-between? Go with what your devs recommend.

+6  A: 

At the end of the day, your developers should not be dictating your technology. This is absolutely a product decision that should be based on your users.

If you are deploying to the consumer Internet, the Flash Player or AJAX is the way to go. If you're deploying to a private LAN for a .net enterprise, you have options.

Luke Bayes
+1  A: 

You seriously shouldn't use ANY of these ActiveX2.0 technologies. Neither Silverlight nor Flex...

First of all, both of them are nothing more then "distributed winforms frameworks with support for being ran in the browser", second of all they don't port well to other devices (specially true for Silverlight), thirdly they don't work good with other portions of your page. They don't work well for disabled people, etc, etc, etc. List goes on into infinity...

Adobe and Microsoft both tries to hide this fact really hard, but at the end of the day both Silverlight and Flex is nothing but ActiveX in a new wrapping...

Sure they run in sandboxes, are managed languages and all that. But it's still a big piece of BLOB being downloaded to run locally in your browser, AKA ActiveX...

Thomas Hansen
I hear this theory often and I have to take issue with it. Do you suggest I develop my first person shooter in Javascript and CSS so that all the teenagers out there running Plan 9 can play it? Enterprise LOB applications can particularly benefit from the deployment and maintenance advantages offered by RIAs. Developing rich content (like a 3d engine for instance) with HTML/CSS/JS is extremely difficult and suffers from square peg/round hole syndrome. RIAs have their place, and I look forward to more competition in this arena.
For your first person shooter JS and HTML is probably not the right technology - today - to use. Though the thing you say about deployment and maintenance in regards to enterprise LOBs requires commenting. To maintain and deploy a silverlight thing is far more advanced and difficult and full of hassle then it is to deploy a "JS and HTML thing"... (obviously!) And Silverlight is probably marginally less hassle to deploy (and maintain) than a desktop thing...
Thomas Hansen
Regarding enterprise apps, HMTL is not an option for the field I work in (resources). The content and functionality required is just too dynamic. For operations with a Microsoft SOE, Winforms was the best option. WPF makes things easier with click-once for deployment, but you still have to deal with the endless bureaucracy of getting desktop apps approved for an SOE. To have something running in the browser under .NET code that does not require the normal haggling with the IT crowd is a joy.
@Alex - It would be interesting to see why you think your domain problems are too complex to be solved with the W3C platform (HTML, JS, CSS, etc) - Google does maps through the W3C platform. Sure some extreme applications (mostly games I suspect) need more power then the W3C platform can supply, but for those kind of things I suspect that something like Qt or NativeClient wold be better fits, if not for anything else then the fact of that they're Open Source. But I might be wrong, maybe Silverlight is just the right thing for you, but then you would belong to a *VERY* small group of devs...
Thomas Hansen
Visualisation engines are the obvious example. And yes, Google Apps and Google Docs look and feel great. Unfortunetely finding that kind of talent in W3C is not easy. Why do you think Flash became so popular in the first place? IMHO it allowed developers to quickly make highly dynamic content without being W3C ninjas. I also cringe at the thought of writing complex applications within Javascript...its not really what it was designed for. If open alternative like NativeClient catch on that will be great, but today I'd have zero chance of getting that approved within my corporate SOE.
@Thomas, JS should be destroyed, its no longer needed after flash and silverlight, HTML is past, and its going to end soon like the Assembly Language, Procedureal Languages etc, people invent technologies to reduce lines of code => man hours for development. Indeed your answer does not even match the question, requester has asked Silverlight Vs Flex, the answer cant be in the form of "stop using both of them"
Akash Kava
"They don't work well for disabled people, etc, etc, etc. List goes on into infinity..." this is wrong, one thing Microsoft always did was they always made good accessibility in all of their products, the UIAutomation Peer technology is far better then any other available in the market.
Akash Kava
+1  A: 

Although I have done work with Silverlight and am pretty excited about the ability to have apps living outside of the browser, one huge benefit of AIR is that is provides access to native drag and drop functionality. This allows you to build very user-friendly image or document uploads features (e.g. Flickr uploader). From what I heard, MS is not focusing on that kind of support yet (i.e. no plans announced).

Philippe Monnet

If you know .NET, Silverlight 3.0 is the way to go. I'm using it and I love it. I don't have to mess with AJAX or JS BTW (I have no idea what that guy was refering to, maybe SL 1.0) For data it's mostly async WCF calls (LINQ to SQL behind WCF) or XML files or RIA Services. It let's you use most shader FX, it has styles, control templates and the native access windows/mac clipboard. I can run high def video and most processes run very well even under slow CPUs. I also enjoy the data binding, control binding and the observable collections save me a lot of time. PLUS i can use LINQ, major time saver, not to mention using Visual Studio to debug with.

I'm developing enterprise .NET applications, so I know my install base and they will install the add-in (30 seconds usually). For a front end website, you may lose some users who don't want to install silverlight or don't run Mac or Windows. You CAN have apps with SL outside of the browser with 3.0.

I may be a biased .NET guy but I've been developing so quickly I have to recommend it.

+2  A: 

i too wonder the same, but this forum is too microsoft heavy, so i view any pro silverlight comment with a bit of scepticism.

+3  A: 

My team used to write rich web features in Flex, and now writes them in Silverlight.

Our reasons for this switch:

  • FlexBuilder is built on Eclipse. Eclipse is awful! Free, but bug ridden, glitch filled and slow.
  • FlexBuilder is twice the price of Expression Blend, which we get for free with MSDN anyway.
  • Flex is a pain to source control, it doesn't like being made to put files in one place and it doesn't play nice with other parts of your solution (we tried with SourceGear Vault and SVN).
  • Flex's version of ActionScript doesn't like most SOAP implementations, in particular it has all sorts of problems with .Net WebMethod ones.
  • Despite us using licensed Flex components periodically it decides that we don't have that version and adds demo-only watermarks in. The only way to remove this is to take the project to bits, reinstall Flex, reinstall the licenses and rebuild it.
  • FlexBuilder does not like Vista at all.
  • Silverlight acceptance is growing, once it was at the level where we could add it as a requirement for the relevant features we switched. If we were working for a web (rather than corporate) audience I'm not sure that we could have.

The rest of our project is .Net and C#, you may find all these issues less significant in a Java shop.

+8  A: 

We are doing both silverlight and flex, and here are developer's point of view for both.

Pros of Silverlight:

  1. Power of C#, Code Snippets, Reusing existing C# Algorithm Implementations
  2. Power of other languages too, Generics and Linq etc
  3. Power of Native execution of CLR instead of Flash's Action Script Interpretator
  4. One Integrated Visual Studio for All Development
  5. Expression Blend is really cool and more advanced editor then Flex Builder
  6. XAML is Search Engine Friendly
  7. Pretty nice state transitions and easy to define them
  8. Threading and Asynchronous Tasks
  9. Accessibility, no one knows that Microsoft always made the best accessiility features on all of its products, they always worked well with disabled people, comparing the browsers only IE supports full accessibility and Safari/firefox etc are no where closer.

Cons of Silverlight:

  1. Strictly Microsoft Platform, I know lot of people will argue but with current scenario, half of Intel Mac guys cant get silverlight 3.0 working, all PPC Mac guys cant use Silverlight 2.0 onwards, and No silverlight for Linux.
  2. There is mono, but not officially supported by Microsoft, it will always lag behind reverse engineering .NET and porting it on other platform, its not out of the box yet.
  3. Majority of components/controls are "Sealed" so its difficult to extend them and override to make new components easily.
  4. Bad CustomControl/UserControl architecture. E.g. you cant have XAML's root as ComboBox or any other control and let it have both design as well as code, you can create custom control but they are way too complex
  5. Binding requires component naming and does not support instance expressions like flex does, though two way binding is good in silverlight but you have to write long codes for multiple bindings for one math expression
// this is possible in flex..
// but not in silverlight
<mx:TextBox id="firstName"/>
<mx:TextBox id="lastName"/>

// display full name..
<mx:Label text="{firstName.text} {lastName.text}"/>

Pros of Flex:

  1. Truely platform independent, supported on various hardware and operating systems and truely working everywhere great.
  2. Open Source makes it really easy to understand and extend the functionality.
  3. Every control/component can be extended and there are less restrictions overriding default behaviour.
  4. The most easy way to create new components, you can have mxml derive from any control and extend them with extensive binding
  5. Flex contains lots of controls and you dont need any third party library

Cons of Flex:

  1. Slow execution for iterative executions, no threads !! no async tasks !!
  2. Based on point 1, no great animation or graphics possible
  3. No generics, No other languages, No linq..
  4. Number class has a bug, cant store full 64 bit long value
  5. Eclipse is bad to design something great UI


  1. We use flex for data applications, those are simple form processing applications
  2. Silverlight for extremely rich graphics and animation
Akash Kava
+1  A: 

Interesting thread. Reasonably well balanced answers/comments. To see what Silverlight can do that Flash could not (lack of multithreading):
For broader discussion on Flash versus Silverlight versus HTML5: search for "silverlight tv 21"

Franck Jeannin