Filtering LinqDataSource

Codes can be downloaded here

The RAD nature of ASP.NET Webforms makes it the sound choice for creating tools and utilities. I’m talking about small applications which aid development and are not intended for production. Among these features, the one that probably saves the greatest amount of time is data binding. I’ve tried all the data sources and with LINQ elegant syntax involving extension methods and lambda’s, I expected that with LinqDataSource, I can apply these new language features during filtering. I’m very disappointed to find out I have to deal instead with something I hated most – string literals!

The page I created is a log viewer which is nothing but a grid and a bunch of controls for the filter values. The illustration here is simplistic but the technique is not compromised in any way. The data is stored in a table with columns for the date the log was made, the level or severity of the message and of course the message. A grid will display this using LinqDataSource.

 

Because it’s an ad hoc filter, I decided not to use the configurable WHERE parameters of the LinqDataSource. I thought I could add parameters as needed at run time. It is indeed possible and after some rummaging, I found out that the best place to do this is in the  LinqDataSource.Selecting event. In this event, the sender is a LinqDataSourceView which exposes a Where string property. This accepts the body of the lambda expression that one usually put in the Where extension method. The only catch: it’s string. Beautiful! The tough part is when dealing with dates because you have to use DateTime utility methods and all this without the benefit of Intellisense. Shown below are the pertinent codes for the sample app you can download for this post.