Convener: Phil Dennis @pjdennis

I have just finished rolling out a small smart-client app to production, and hosting a discussion on Smart Client architecture in light of that experience. The technologies I used:

• POCO domain model
• NHibernate for data access
• Service layer exposed using WCF
• WPF with MVC architecture for client-side presentation

As a starting point for discussion, here are some "rules" for Smart Client development. These are things we get "for free" to some extent, in web applications:

1. All access to external resources should Be done via a physically separate service layer:
• Enables proper security
• Enables scalability
• Simplifies deployment
2. No out-of-process calls from within UI event handlers
• Goal: responsive user interface
• Implementation: Asynchronous access to the service layer
3. Minimize consecutive calls to the service layer - A single user action should result in a single call to the service layer
• Goal: Minimize latency of the user interface
• Enables atomicity of updates, e.g. to a database

Tools Mentioned:

• MassTransit
• NServiceBus

Concerns:

• Working disconnected
• synchronization
• security and impact on the client (trust levels, deployment)

Why WPF over WinForms:

• seems like future tech, Microsoft is going more this way (VS2010)
• better data binding story
• auto layout capabilities

Architecture (examples):

• Shared domain layer across all tiers (service, DTO, client all use the same classes)

WCF:

• for communications
• challenges: IEnumerables are not supported for serialization, stick with out of box settings
• blog post series on implementing command pattern over WCF: http://davybrion.com/blog/2009/11/requestresponse-service-layer-series/