ASP.NET 4 Unleashed

Querying with the CustomExpression

Although the QueryExtender is all about giving you the ability to do your filtering declaratively, occasionally you just need to resort to using a little bit of LINQ to get the job done. However, if you need that bit of LINQ to work in tandem with other expressions already modifying a query, you can make use of the CustomExpression class.

This works simply, you just supply a method to be invoked during the query process that enables you to inject your own modification to the query pipeline. Below is a snippet showing a custom expression and the C# method invoked by this custom expression. Although you wouldn’t normally use the custom expression to perform such trivial filtering, this at least gives you an idea ...