Sunday, March 1, 2009

Things to CodeGenerate besides the Data Access Layer

[This was originally posted at]

CodeSmith is a powerful code generator (worth its weight in gold). And while one of the most popular things to automatically generate is the data access layer, there's a lot more to CodeSmith than just wrapping databases:

  • System data - Given an xml file, you can generate all your interrelated system data. For example, say your application has a data-driven relationship of groups, roles, menu items, tabs, and such (i.e. security and navigation) - you could write tons of tedious and brittle SQL scripts, or you could abstract it to an xml file and generate the SQL scripts from that.
  • Data Structures - Especially before Generics in .Net 2.0, CodeSmith was popular for its strongly-typed collections (much faster performance than boxing and unboxing an ArrayList). You could make other data structures as well, depending on your application's need.
  • Documentation - While CodeSmith's default DataDictionary template is popular for documenting your database schema, you could use CodeSmith as a Super-XSLT to transform any arbitrary xml list (like a file containing business rules, config, or test cases), into human-friendly HTML reports.
  • Domain-Specific-Language - It's often more efficient to work at a higher level of abstraction. So, you could write an xml script, and use CodeSmith to translate that ("compile?") into useful actions.
    • Say you were trying to write automated UI tests, but the UI technologies keep changing, so you write a simple abstract xml script for the basic actions you care about (Load page, click button, etc...), and CodeSmith transforms that into the UI testing code for the relevant testing framework.
    • You could write abstract tests in xml (i.e. the data for pairs of input and output), and then use CodeSmith to dynamically generate all the unit tests from that.
    • You could read your file system to create an MSI installer using something like Wix.
  • Starting Templates - I favor active re-generation when possible, and there's a balance between what to code-generate vs. what to refactor, however, sometimes it's useful to passively generate a starting template - just to give you a head start. For example, say your UI is too complicated to actively re-generate, but you could take an xml file of input and generate a stating template, from which you could then modify.

Basically, CodeSmith lets you take any input (a database, xml file, your file system, etc...) and generate any text output (sql, xml files, C#, aspx, html, js, etc...), and then also call C# to do anything on those files (install them in the database, commit it to source control, execute the resulting C#, etc...). It's a beautiful thing.

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