No HTTP request occurs when calling WCF Service from Silverlight client

Question

While debugging an issue with an old Silverlight application, I narrowed down the problem to a particular WCF service call, which looks something like:

_serviceClient.UpdateFooAsync(fooDto);

This code hasn't been changed in years, and it has largely worked as expected. With one specific entity, however, the call fails silently. The asynchronous invocation occurs as usual, but no corresponding HTTP request occurs and the handler that would fire when the event completes -- erroneously or otherwise -- is never invoked.

Here are some additional details:

• The app uses Silverlight 5.
• The app's service client is an auto-generated client that inherits from System.ServiceModel.ClientBase<T> .
• The service uses WCF and .NET 4.0.
• When the call occurs, no corresponding entry is written to the WCF trace log.
• The service uses a BasicHttpBinding . I tried increasing all the quotas and limits to their maximum values but it didn't help.
• The entity I'm trying to send to the service is about 600K in size when serialized to XML/SOAP format. It's large, but well within the limits currently configured on the endpoint.
• I have confirmed using multiple tools that no HTTP request occurs.

Because this issue is happening only in the case of one specific entity, I can only assume some aspect of that entity is to blame, but I've been unable to spot whatever that is.

Answer 1

The Http Activation option must be enabled on the server features, inside the .NET framework and WCF services. This options may be disabled during some update.