Why don’t Beta 2 sites work on RC0 – Question of the Day

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I've been getting a lot of questions and confusion around why you get the following strange behavior.

"I've installed the RC0 developer runtime, and whenever I hit a Beta 2 site, I get the 'install badge' instead of my site. If I click this badge to install I can't because I'm told I already have a newer version. What gives?"


When the browser sees an <OBJECT> tag, it looks at the type parameter to see what it should use to render the object. Silverlight Beta 2 uses the following: type="application/x-silverlight-2-b2" , Silverlight RC0 (and later RTW) uses the following: type="application/x-silverlight-2"

So, if you have RC0 installed, and you hit a beta site, the browser sees the '-b2' type tag, and doesn't have a Silverlight object that understands it, so it renders the install badge (as per the rules in Silverlight.js), and this install badge links you to the B2 installer. As you have a newer version, you get an error.

RC0 is a developer runtime, so there is no public link to it, and the badge links to the end user runtime of Beta 2. When we RTW the link will be updated to the RTW end user runtime, and the problem will go away.

The process to follow, for your own site is to recompile it with the RC0 tools, and to change the type tag to the RCO/RTW tag, and then test it.

If you want to view other people's sites, then you'll need to have Beta 2 installed.

Remember, that ALL Beta 2 sites will break  with the RTW runtime, at the very least with this type issue.

RC0 is available to download here: http://silverlight.net/getstarted/sl2rc0.aspx

Comments (8)

  1. I’ve been getting a lot of questions and confusion around why you get the following strange behavior

  2. You’ve been kicked (a good thing) – Trackback from DotNetKicks.com

  3. vbroto says:

    This post is a rationalization. We understand that the runtimes are not compatible. The question is then, why the SL2 runtime is not backward compatible with Beta2?

    Or, why my project of the last 6 months has to be reworked?

  4. There are very many breaking changes between SL2B2 and SL2RTW.

    Beta 2 was, as its name suggests, a Beta, and was never announced as feature complete. Through feedback on usage of the product from many avenues we made changes to provide the best product possible — which of course leads to breaking changes.

  5. Following Jesse’s and Pete’s excellent posts on porting Silverlight2 apps from Beta 2 to the final release

  6. joe2000 says:

    I use Silverlight 2 beta 2 in sharepoint 2007, How to change B2 tag to RC0 in SharePoint 2007?


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