I'm working on a Silverlight based application. We've recorded the scripts using Load Runner 11.5 and while replaying to find dynamic values for correlation, we found out that the entire data in a business step is being stored in a BLOB (BinaryLargeOBject) and sent over an HTTPS request. The application uses BasicHTTP Binding with Windows Authentication.

We are using Fiddler to capture the Request-Response XML and from them, we are trying to create Web Custom Requests.

But the stumbling point for the entire scripting is the BLOB Object which we are unable to correlate.

As an alternative, we also tried Web Services Protocol but we are getting "Expected SOAP Result, Received SOAP Fault" with an HTTP 500 Error.

SOAP UI was also not able to launch the WSDL. It kept on loading.

Since it's a Silverlight based application it's bound to use a lot of caching. Is our approach correct in load testing a Silverlight Application in the above-mentioned ways?

Cause I feel that the entire application is downloaded to the Browser cache/temp files and then any further communication is carried out in the form of BLOBs over HTTPs Request.

Any help in this regard is deeply appreciated.

  • 1
    It sounds like your assumption is correct. I don't know that there is a way. After 1,329 views over 4 years I think this might be a no-win situation except to work with it in the BLOB the way it functions. Did you try asking LoadRunner directly? Any update on this issue and if you found a way to work around it?
    – mutt
    Aug 9, 2017 at 15:46

1 Answer 1


It sounds like you are having difficulty scripting and testing the performance of a Silverlight-based application using Load Runner and Fiddler. Correlating dynamic values in a Binary Large Object (BLOB) can be a challenging task, as the data is not easily human-readable.

One approach you can try is to use a tool that can decompress and decode the BLOB data, such as a hex editor or a specialized BLOB analysis tool. This may allow you to extract the dynamic values and manually correlate them in your script.

Alternatively, you may want to consider using a different tool or approach for testing the performance of your Silverlight-based application. Some options to consider include:

Using a tool that is specifically designed for testing Silverlight applications, such as the Silverlight Performance Analyzer. Using a tool that can interact with the GUI of the application, such as Selenium, to automate the creation of performance tests. Using a network traffic capture tool, such as Wireshark, to analyze the network traffic between the client and server and identify patterns that can be used for correlation. It is also worth noting that testing a Silverlight-based application can be more challenging due to the use of caching and the fact that the application is executed within a browser. You may need to take this into account when designing and executing your performance tests.

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