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He has a WCF Header… Get it !

Often, you’ll need to pass some piece of information on some or all of your  WCF Service operations. For my team, we had recently exposed some functionality in an old WCF Endpoint via a Web Front End and wanted to log some auditing information on each and every Service Call. Obviously modifying every single method signature to accept the new parameters would be a pretty significant breaking change to all the consumers so instead we looked at passing this information as a Custom WCF Message Header. WCF exposes a number of interfaces which you can leverage to inspect & modify messages  on the fly and to add customer behaviors to service endpoints. In the following demo, we’ll go through the process of building a Custom Header for our WCF Service & subsequently passing that information from the Consumer Client back to the service. In our contrived example I’ll be attempting to pass 3 pieces of information to the WCF Service as part off every message call.

  • The username of the currently logged in web front-end user
  • Since our website is deployed across multiple nodes, the id of the web node
  • The “Special Session Guid” of the current users Session
Important!The completed solution can be found on GitHub at   
This scenario could apply to a number of other real world situations. Perhaps the service is secured and called using a single WS Security Account, but we need to log the user who’s session, the service call originated from on every service call. Or perhaps you’re exposing your service to the public and as well as providing a username & password to authenticate, the caller also needs to provide some sort of “Subscription Account Number” in addition to their Credentials. Any of these scenarios are candidates for adding a custom header to a WCF Service.

The Quick & Dirty Solution

Of course I could just edit method signatures of each service call to accept this additional information as additional parameters but this causes a number of other problems. This might be feasible for a small in-house service, or dummy application but it causes a number of issues in reality.
I need to add additional parameters to every service call which isn’t a particularly elegant solution If I need to add more information in the future, I must edit every service call signature which at worst is a breaking change for every client and at best, a significant amount of work & re-factoring. Depending on the scenario, I’m potentially intermingling Business Logic with Authentication/Authorization or some other sort of Service Wide Validation logic which is going to increase the complexity of any future re-factoring.

Operation Context & Custom Message Headers

A better solution would be to “tag” each service call with some sort of header information. In this way, we could piggy-back our additional data along without interfering with the individual method signatures of each service call. Thankfully WCF includes built-in support for MessageHeaders. The services OperationContext includes Incoming & Outgoing Message Header collections.

//Service Contract

endpoint security manager 3     gfi endpoint security 2013 keygen
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