Silverlight 2.0 – Silverlight Apps calling asmx web services

A while back I worked on a Silverlight application that was hosted in SharePoint. The Silverlight application was to call a web service written by a third party vendor in .NET 2.0.

Problem
As what we all normally would do in a Silverlight app is to call this web service. However, I got the following error when my application tries to call the asmx web service:

“An error occurred while trying to make a request to URI 'http://localhost:1000/webservice.asmx'. This could be due to attempting to access a service in a cross-domain way without a proper cross-domain policy in place, or a policy that is unsuitable for SOAP services. You may need to contact the owner of the service to publish a cross-domain policy file and to ensure it allows SOAP-related HTTP headers to be sent. Please see the inner exception for more details.”

Solution

After some research, I found a recipe to get it going again:

1. Create a new file within the web service application (at the root of the requesting domain), called clientaccesspolicy.xml with the following contents:
   
   
   <?xml version="1.0" encoding="utf-8"?>
   <access-policy>
   <cross-domain-access>
   <policy>
   <allow-from http-request-headers="*">
   <domain uri="*"/>
   </allow-from>
   <grant-to>
   <resource path="/" include-subpaths="true"/>
   </grant-to>
   </policy>
   </cross-domain-access>
   </access-policy>
   
   
   
2. Create another file within the web service application(at the root of the requesting domain), called crossdomain.xml with the following contents:
   
   <?xml version="1.0" encoding="utf-8"?>
   <cross-domain-access>
   <allow-http-request-headers-from domain="*" headers="*"/>
   </cross-domain-access>

After adding these policy files, my app started working. Hope this helps.

References

http://timheuer.com/blog/archive/2008/04/06/silverlight-cross-domain-policy-file-snippet-intellisense.aspx

http://timheuer.com/blog/archive/2008/06/10/silverlight-services-cross-domain-404-not-found.aspx