Controlling authentication with the WF 3.5 SendActivity

Someone emailed me a question about whether or not you can specify credentials when using the OOB SendActivity in WF 3.5 because they heard that you had to write a custom activity to accomplish this.  You do not have to write a custom activity.  While it is true that the SendActivity links to a named endpoint, and if you use the configuration file to configure your endpoint you can't specify specific credentials (a username and password for example),  WF 3.5 has a OOB WorkflowRuntime Service named the ChannelManagerService.  The ChannelManagerService (which I described in my article on MSDN - here http://msdn.microsoft.com/en-us/library/cc626077.aspx)  allows you to pre-populate some or all of the endpoints you want the SendActivities running inside of your WorkflowRuntime to use.  So you definitely can programmatically configure an Endpoint that the SendActivity can use without having to write a custom activity.