Today I completed a webcast as part of a 15 part series - today's subject concurrency, throughput and throttling. I received some questions about callback and Windows client applications that I thought I would elaborate on here. In fact, I went a little overboard and created a bunch of samples that would illustrate the behavior of services and clients when you have a Windows client, a service with a callback contract (thus, two-way communication) and various WCF settings at the client and service that relate to concurrency, multithreading, synchronization with the UI thread, and so on.

The following table summarizes various settings at the client, service and callback and the resulting behavior at runtime. Here's the breakdown for each column:

• Callback Sync Context - refers to the UseSynchronizationContext setting for the CallbackBehaviorAttribute on the client callback object.
• Callback Concurrency Mode - refers to the ConcurrencyMode setting for the CallbackBehaviorAttribute on the client callback object.
• Service Operation - Indicates if the service contract operations are one-way or two-way.
• Callback Operation - Indicates if the callback contract operations are one-way or two-way.
• Service Concurrency Mode - refers to the ConcurrencyMode setting for the ServiceBehaviorAttribute on the service type.
• Resulting Behavior - when the corresponding sample is run, what happens?

I have also uploaded sample code for each of these scenarios, numbered in order of table row description below. Get the code here.

Here is a summary of considerations.

• Contract design:
  • Make callback operations one-way. If this isn’t possible, make the service reentrant. Prefer one-way callbacks since most likely the service doesn’t care about responses.
  • If service operations will notify clients with a callback, make them one-way as well.
• Exception handling:
• Remember that uncaught exceptions invalidate service, client and callback channels where sessions are involved. Two-way communication can only happen over duplex, thus there is a transport session (TCP, named pipes) or HTTP session (using reliable sessions over WSDualHttpBinding). 
• Throw faults for known exceptions unless you want the client to be forced to recreate the proxy and start a new session. That includes clients – who should not allow exceptions to flow back to the service during a callback unless they intend to destroy the session.
• To avoid destroying the session: if callback operations are one-way, swallow the exception after handling it at the client; if callback operations are two-way, report a fault to the service in response.
• Windows client issues:
  • Always disable synchronization with the UI thread for callback objects, by setting UseSynchronizationContext to false in the CallbackBehaviorAttribute. 
  • Multithreaded clients should invoke services on another thread (can use asynchronous proxies) when callbacks or long running service operations are involved. This prevents UI thread from blocking during call, allows callbacks to communicate freely with UI.
  • Use Invoke() to communicate with UI from the callback thread. 
  • Don’t forget to protect other client state if the callback object supports multiple concurrent callbacks. That means the ConcurrencyMode setting is Multiple in the CallbackBehaviorAttribute.

In preparation for our upcoming .NET 3.5 Roadshow  (http://www.dotnetroadshow.com/) I am posting setup instructions for those who need some tips on setting up an environment to work with the latest technologies. If you can start using Visual Studio 2008 (Beta 2 available now), I highly recommend it - it gives you the latest .NET 3.0 tools for your WCF, WPF and WF projects. But, for those still using Visual Studio 2005, I have provided those links here as well.

• Windows XP/SP2 or Windows Server 2003
  • Enable IIS
  • Enable MSMQ
  • Install .NET 3.0
    • http://www.microsoft.com/downloads/details.aspx?FamilyId=10CC340B-F857-4A14-83F5-25634C3BF043&displaylang=en
• Windows Vista or Windows Server 2008
  • Enable IIS/WAS
  • Enable MSMQ
  • NOTE: .NET 3.0 is already installed
• Windows SDK for .NET Framework 3.0
  • http://www.microsoft.com/downloads/details.aspx?familyid=C2B1E300-F358-4523-B479-F53D234CDCCF&displaylang=en
• SQL Server 2000/2005 or SQL Express
• SQL Server 2005 SP2 (if applicable)
• If you use Visual Studio 2005, install these add-ons:
  • Visual Studio 2005 Extensions for WCF and WPF – Nov 2006
    • http://www.microsoft.com/downloads/details.aspx?FamilyId=F54F5537-CC86-4BF5-AE44-F5A1E805680D&displaylang=en
  • Visual Studio 2005 Extensions for WF – Nov 2006
    • http://www.microsoft.com/downloads/details.aspx?familyid=5D61409E-1FA3-48CF-8023-E8F38E709BA6&displaylang=en
  • Visual Studio 2005 LINQ CTP – May 2006
    • http://www.microsoft.com/downloads/details.aspx?familyid=1e902c21-340c-4d13-9f04-70eb5e3dceea&displaylang=en
  • Visual Studio 2005 ADO.NET vNext CTP – May 2006
    • http://www.microsoft.com/downloads/details.aspx?FamilyId=B68F6F53-EC87-4122-B1C8-EE24A043BF72&displaylang=en
  • Visual Studio 2005 Entity Data Model Designer Prototype CTP – May 2006
    • http://www.microsoft.com/downloads/details.aspx?FamilyID=74bda7b2-9ca9-4eea-a33f-31942ddc9dbe&displaylang=en
    • NOTE: this doesn’t work so well, better to install VS 2008 Beta 2 extension for this
• If you use Visual Studio 2008 Beta 2 (preferred), install these add-ons:
  • .NET 3.0 tools are built-in to VS 2008
  • LINQ and related tools are built-in to VS 2008
  • At the time of this writing the Entity Data Model and related tools were not available for Beta 2.

On my newest machine, I have a fresh installation of Windows Vista Ultimate that I installed Office 2007 to. After running Outlook 2007 the first time, Office 2007 goes through a configuration step that requires a reboot, but I received this error:

Error 1719: The Windows Installer service could not be accessed

There is an updated KB entry with recommended steps to fix the problem here: http://support.microsoft.com/kb/315346/en-us

This entry doesn't mention Vista at all, and in fact, I was able to repair the problem on my Vista machine just by running the following command line instructions, in this order:

msiexec /unregister

msiexec /register

So, if you have this problem, give that a go first...then consult with the KB entry if you still have issues.

I delivered 15 webcasts on WCF this summer, from July through September. Each webcast is 1 hour in length, touching on the fundamentals and practical approaches for your WCF development efforts. Here are the links to the archived webcasts!

NOTE: On page 3 of the registration process you can print the slides.

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 01 of 15): Overview

Monday, July 02, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344312&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 02 of 15): Contracts

Monday, July 09, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344314&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 03 of 15): Contract Versioning

Wednesday, July 11, 2007 10:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344318&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 04 of 15): Exceptions and Faults

Friday, July 13, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344322&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 05 of 15): Bindings

Monday, July 23, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344330&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 06 of 15): Hosting

Wednesday, July 25, 2007 10:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344338&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 07 of 15): Messaging Patterns

Friday, August 10, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344342&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 08 of 15): Instancing Modes

Monday, August 13, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344344&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 09 of 15): Concurrency, Throughput, and Throttling

Wednesday, August 15, 2007 10:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344346&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 10 of 15): Security Fundamentals

Friday, August 24, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344348&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 11 of 15): Federated Security

Monday, August 27, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344351&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 12 of 15): Reliable Messaging

Wednesday, August 29, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344353&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 13 of 15): Transactions

Monday, September 03, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344355&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 14 of 15): Message Queuing

Wednesday, September 05, 2007 9:00 AM Pacific Time (US & Canada)

o http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344357&Culture=en-US

· MSDN Webcast: Windows Communication Foundation Top to Bottom (Part 15 of 15): Extensibility

Friday, September 07, 2007 9:00 AM Pacific Time (US & Canada)

http://msevents.microsoft.com/CUI/EventDetail.aspx?EventID=1032344359&Culture=en-US

A big thanks to everyone who attended my two sessions at Tech Ed Orlando on CardSpace. I also really enjoyed all of the great questions during and after each session, I can see a lot of momentum building around CardSpace, other identity selectors and providers, and approaches to federated identity models. Very exciting stuff indeed.

As for my code, as I said I had already posted the code beforehand, but I have updated the ASP.NET sample slightly to reflect how I associated the username and password with a unique identifier for a personal card. You can download the latest version of my CardSpace samples here.

Enjoy!

Please see this updated post from the Dev Connections conference in Orlando (just past) for the code samples and references for the performance talk I stepped in to do. Some people were asking me about the post, and the update had not shown up on the blog...now it is there :)

See this link.

This is great news from Soma's blog. Now Expression Web and Blend (soon) will be available to MSDN Premium subscribers. Many of us have been hearing feedback on the subject and relaying this feedback to Microsoft...nice to know they are listening!

http://blogs.msdn.com/somasegar/archive/2007/04/03/listening-to-your-feedback-expression-and-msdn.aspx

Once again a fantastic conference in Orlando. Dev Connections just keeps getting better and I always enjoy being part of it. Not to mention the weather in Orlando isn't bad!

Here are links to my code samples for each talk I delivered. Enjoy!

.NET Technology Roadmap Tutorial

• This tutorial provides an overview of all the key Microsoft technologies for today, tomorrow and the forseeable future - to help you understand and weigh choices for building web, windows and SOA applications.
• Links to the tutorial code can be found in this blog entry (keep an eye out for updates, additions over time):
• http://www.dasblonde.net/2007/03/23/MakingSenseOfTheMicrosoftTechnologyAvalanche.aspx

ASP.NET and WCF

• All of my WCF samples for my book can be found here: http://www.thatindigogirl.com/LearningWCFCode.aspx

ASP.NET and CardSpace

• Demonstrations in this talk can be found here:
  • http://www.dasblonde.net/downloads/code/CardSpaceSamples.zip

WCF Federated Security

• My claims-based samples can be found here:
  • http://www.dasblonde.net/downloads/code/ClaimsBasedSamples.zip
• And, my STS sample here (NOTE: this sample will be updated shortly with an upcoming article, stay tuned!):
  • MediaServicesFederation.zip (2.07 MB)

 WCF Contracts and Versioning

• All of my WCF samples for my book can be found here: http://www.thatindigogirl.com/LearningWCFCode.aspx
• See ServiceContracts, DataContracts and AdvancedSerialization directories.

ASP.NET Performance (Updated 06/07/2007)

Ok people, I had this in my Windows Live Writer to send a long time ago, and somehow it did not post...but since I haven't posted in a while I didn't notice. Many apologies for the delay. Does the "better late than never" statement apply here? I hope so...

• In this talk I covered a lot of ground, and theory around performance including simpler performance tips, the progression of asynchronous handlers to component distribution, and the importance of performance counters for your SLAs.
• You can look at my ASP.NET Sandboxing articles and samples for more resources on component distribution.
• ASP.NET Sandboxing - Part 1
• Code updated for ASP.NET 2.0: ASPNETSandboxing_updatedfor2.0.zip 
• ASP.NET Sandboxing - Part 2
• Code updated for ASP.NET 2.0: ASPNETSandboxing2_updatedfor2.0.zip
• See also the following data demos for examples of data caching
• DataDemos.zip
• DataAccessComparison.zip (this is a simple demo illustrating performance benefits of data reader over data set)
• My LocalizedGallery globalization example (posted here) illustrates the use of complex output caching based on custom caching by browser, culture and profile
• Asynchronous HTTP handlers:
• Rick Strahl did a great job documenting ASP.NET 2.0 threading model here
• Jeff Prosise and Fritz Onion wrote in-depth articles on the subject for 1.1 and 2.0 as well
• Here is an example showing how to create custom performance counters:
• PerfCounters.zip
• Here is an example illustrating some of the health monitoring configuration features of ASP.NET 2.0:
• HealthMonitoring.zip