Vishful thinking…

Bing map issues with IE6 & Silverlight 2 / ESRI Silverlight API 1.0

Posted in ArcGIS, ESRI, Silverlight by viswaug on August 17, 2009

I have been having troubles for a while now getting the Bing map layers to show in IE6 with the Silverlight 2 installed. Unfortunately, when I got down to the bottom of it, it turned out to be a bug in Silverlight 2 that actually prevents the Bing map layers to show in the ESRI Silverlight API 1.0 map control. Initially, I wasn’t sure why the bing map layers where not showing up on just the IE6 browsers but displayed and worked just fine on IE7+ and Firefox. To check the issue for yourself, if you are using an IE6 browser with the Silverlight 2 plugin, just browse over the Bing maps demo site setup by ESRI to check it out for yourself. you will see the error message shown below.

Part of the error message displayed above in the alert window (“Make sure you are generating a VE token from the same token service as the VE Layer ServerType: Staging or Production”) is actually not accurate. The demo site simply handles the ‘InitializationFailed‘ event on the Bing TileLayer and displays the message above not matter what the error actually was. This had mislead me initially and had sent me hunting for clues in the wrong direction. One other weird I noted here in the ESRI Silverlight API 1.0 is that the event arguments for the ‘InitializationFailed‘ actually doesn’t provide you with the error information. But the error information is actually available in the ‘InitializationFailure‘ property of the layer which I thought was a little confusing. Hoping this will change in the next versions of the API.

After spending a lot of time on fiddler, snooping around the requests made to the Bing servers & searching the web, I finally figured out the reason why the Bing layers do not show up on the map. The reason turned out to be a bug in the Silverlight 2 plug-in in IE6. The error had to do with Silverlight 2 plug-in in IE6 having troubles handling compressed content returned from the server. More details about the bug can be found here. Since the compressed content in this case comes from the Bing servers, I had not control over it at all and thus it eventually turned out that the problem couldn’t be solved in a good way. But there was an advanced setting in IE6 that I could turn off to get the bing layers to show up in the map. Under the ‘Tools’ menu in IE6, select the ‘Internet Options’ item. In the ‘Internet Options’ dialog, click on the ‘Advanced’ tab and in the settings disable the ‘Use HTTP 1.1′ option.

But this workaround does have its own drawbacks of not being able to use some of the advanced HTTP 1.1 capabilities like compression etc. So, please be mindful of it before adopting the solution.

Some salvaging facts,

  • This bug has been fixed in Silverlight 3. So, users who are still using IE6 but have upgraded to the Silverlight 3 plug-in will not have this problem.
  • IE6 is losing market share – (though a good chunk of the users on the web still use IE6)
  • The Silverlight 2 plug-in is no longer available for download from Microsoft.
  • Windows update upgrades user with Silverlight 2 to Silverlight 3.

But, if you are writing a public application using the ESRI Silverlight API 1.0 that needs to support Silverlight 2 plug-in on IE6, you definitely might want to consider the above issue and display a message to you users asking them to upgrade or turn off the ‘Use HTTP 1.1′ option in IE6.

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