Performance testing a Silverlight application is more challenging than testing over HTTP. The reason for this is that the server constantly updates the application asynchronously using binary protocols such as Binary XML (MC-NBFX) and binary SOAP (MC-NBFS ) - without reloading the page.
Running a Silverlight test needs a performance testing tool such as NeoLoad which supports the binary protocols and is able to inject the necessary identifiers into the server communication stream.
Silverlight uses identifiers for communication between the client and the server - a mix of application-specific and Silverlight-specific parameters. One of the challenges of running a Silverlight test is that these identifiers change for each communication session. A test tool which simply plays back recorded Silverlight traffic will fail due to the incorrect identifiers. Using the Silverlight test module, NeoLoad is able to extract and re-inject the appropriate values of these parameters during runtime.
NeoLoad converts the binary-format Silverlight requests into XML in order to modify the request parameters by injecting NeoLoad variables, extract content from a response, and set response validations. Microsoft developed Silverlight to deliver rich internet applications (RIA). Testing the performance of Silverlight applications manually is very time consuming. NeoLoad substantially reduces the effort in running a Silverlight test through the use of its protocol module