MessagePredicate Policy Assertion Handler

The WSE 2.0 Technology Preview introduced support for WS-Policy and writing custom policy assertion handlers.

WS-PolicyAssertions is another policy-related specification that defines some standard policy assertions most Web services would want to use. One of these assertions is called MessagePredicate. MessagePredicate allows you to assert arbitrary expressions written in one of two dialects: XPath and SOAP message parts. Hence, with MessagePredicate, you could implement a business rules validation scheme (like the one I provided here) without writing a single line of code. Overall, I find this to be a much better way of taking care of validation needs.

Unfortunately, the WSE2 TP doesn't currently support MessagePredicate. This sample illustrates how to write a custom policy assertion handler that provides MessagePredicate support. For more details, check out my upcoming MSDN Magazine article titled "WS-Policy and WSE 2.0 Assertion Handlers".

Download here.