The Lights Witch Project(s)

Did you know that when you create a new LightSwitch Application project beneath the Data Sources and Screens “Folders” live 5 projects in total?

Changing your view to File View only “reveals” 3 of them: Client, Common, Server. If you choose to Show All Files  2 more appear: Client Generated, Server Generated. Now you have 5 projects in all. Ok, hurry back to Logical View, pretend you didn’t see this.

Seriously now, the reason I include the beginners tag in posts like this one and this one, is because I am trying to make a point. LightSwitch is NOT the new Access. It’s much, much more than Access in terms on both potential but also complexity. LightSwitch Team has done a great job making the Logical View a user-friendly powerful application design environment. But, I believe it’s good to have a broad (at least) idea of what actually happens under the surface. This way when, for some reason (not very probable if you play with the designer only but always possible), you get a build error and clicking on that error a code file you have never seen before appears, you will not be terrified by the fact that someone has turned your beautiful screens and tables into ugly, messy code files.

Client Project: Is the project where the client application and accompanying code is found. In this project, in the UserCode folder, partial classes are automatically created and then populated by code every time you choose (for example) to Edit or Override Execute Code for a screen command. You also put your own classes there (but this is not beginner stuff…). It, very broadly, represents the presentation tier of your application.

Common Project: Is the project where business logic lies. Well, “Business Logic” has always been a bit vague to me as deciding what is business logic and what is not, is a bit foggy. I mean, deciding if a command can be executed under specific conditions or not is business or client? Client is the politically correct answer. To me this has always been a convention of thought. Anyhow Common contains all code that should be available both at the client and the server. One example is writing code for <Entity Name>_Created. This code is executed either at the client or at the server, hence Common.

Server Project: Is the project where the web application and the data-tier lies. An example would be <Entity Name>_PreprocessQuery methods when overridden, the code is included in Server\UserCode\<DataSource Name>Service.cs.

Client/Server Generated are complementary to the respective projects containing auto-generated code that you should never edit in any way (any change will be lost during the next build or modification made by the designer) and this is the reason why the are not visible in File View by default.

It’s better to know the enemy…