WCF and WF are both frameworks. Specifically this means they are not full blown products but rather blocks of utility code with which to build products. For both of these frameworks the hosting process is undefined and it is up to you to provide this. As .NET based frameworks the host can be any .NET process so what are the advantages and disadvantages of each? In this the first of two articles I'll look at options and issues hosting WCF then in the next article I'll do the same for WF.

WCF Console Hosting

Console apps are useful for testing things out and can be useful for mocking up a service if you are testing a client. However, they are not suitable for production systems as they have no resilience associated with them.

WCF Smart Client Hosting

Useful for peer to peer applications.

WCF Windows Service Hosting

This is a tangible host for  production services. Whether this is the best host depends on a number of questions:

• What operation system am I running on?
• What network protocols do I need to support?
• Do I need to execute any code before the first request comes in?

Assuming you want to run this on a server OS and one that is currently released you will have to use Windows Server 2003 (.NET 3.0 isn't supported on Windows 2000 or earlier). If you want to use any protocol other HTTP or you need to execute code before the first request comes in you must use a Windows Service to host your WCF service.

If you are happy to run on Vista or Windows Server 2008 Beta (formally known as Longhorn Server) then you should only use a Windows Service if you need to execute code before the first request arrives.

WCF IIS Hosting

IIS should be your host of choice for WCF services. However, there are two issues to be aware of:

1. IIS6 and earlier can only host services that use HTTP as a transport. IIS7 introduces the Windows Process Activation Service that allows arbitrary protocols (such as TCP and MSMQ) to have the same activation facilities as HTTP.
2. IIS provides activation on the first request. If you need to execute code before this (for example if you have a service that records trend data over time for some external data source and your service queries this trend data) then you cannot use IIS as a host without adding out of band infrastructure to bootstrap the application by performing a request.

So the options for WCF hosting are pretty straightforward. In the next article we'll see that the hosting options for WF have some issues that may not at first be obvious.

Just sitting in on a session on extending the WF rules infrastructure given by Moustafa Ahmed. Some interesting ideas. I especially liked the infrastructure for decoupling the rules from the workflow assembly using a repository, custom workflow service and a custom policy activity. He also showed a custom rules editor that was business user friendly (which the OOB one isn't) called inrule which looked pretty good.

So I'm here at TechEd 2007 enjoying the humidity of Orlando in June. I delivered a Precon on WCF and WF on Sunday with Jon Flanders which was a blast. Mark Smith who writes our WPF course asked me to check out what I could find out about Acropolis - a new framework for creating WPF applications. The Acropolis website went live on Monday and so I wandered over to the boothe to see what I could find out. It came as quite a surprise that Dave Hill, who i used to work with in the UK about 8 years ago, was on the stall. Dave is the architect on Acropolis - its a small world. I had lunch with Dave and it looks like they have some interesting ideas for helping to enforce separation between the presentation layer and business funtionality in an application and it is all expressed declaratively in XAML. If you're building smart clients in WPF its definitely worth keeping an eye on.

After suffering the pain of using BlogX as a blog engine for some time, I have finally moved my blog on to a current engine - namely dasBlog. Hopefully a more accessible engine will get me blogging more regularly