ASP.net Expression Builders 3 - In the web.config file

The final piece of the puzzle to get an Expression Builder working is the entries that are required in the web.config file. Assuming that your expression builder class is in the App_Code directory, the following is all that's required:

      <expressionBuilders>
        <add expressionPrefix="L10N" type="LocalisationExpressionBuilder" />
      </expressionBuilders>

That gets placed in the <configuration><system.web><compilation> node of the web.config file and points to the LocalisationExpressionBuilder type that was previously created.

It's really that simple.