From DataTable to DataContract

For the last four months, I have been very busy porting a large SaaS application from the traditional ASP .NET + Ajax platform to Silverlight 4. This application has a quite standard architecture with a data access layer that talks to the database and exposes a simplified interface to the business level. When a piece of data is required, you just need to call a given method with the appropriate parameters and you usually get back a DataTable object with all the data you need. This is a very flexible scenario because you can directly bind to an ASP .NET control or, if you need to further massage the data, transform the data in memory before binding it.

This architecture became a bit of a problem when I started to port the application to Silverlight because it just does not understand ADO .NET, so it is useless to try to marshal a DataTable object through a WCF web service. Because we needed to keep the "old" ASP .NET application running, there was no point in rewriting the old DAL code so a decision was made to keep it and reuse it as a data source for the new WCF web services. This meant writing a lot of boring code to implement the new DataContract classes. When you create a Silverlight-enabled WCF web service, you must send and receive all your data through strongly-typed classes that are very neatly marshalled over between the two endpoints.

I tackled this issue by starting to write all the new DataContract code by hand... until I got bored. The process is incredibly boring, time-consuming and error-prone. After a few weeks at it, I found out that writing all the WCF plumbing was taking a large portion of every ported feature, so this needed a closer look. What could I do to help me bridge the gap between the existing, tried and true DataTables and the new DataContracts?

A code generator.

The idea is quite simple: plug in a piece of code that takes either the freshly-created DataTable (or DataView) and generates a text file containing C# code that declares two DataContracts: one for each row and another for the whole list of rows. Oddly, this code must run on your web server, so it is best suited for your development environment only. To make my life easy, I created a single extension method to the DataTable and DataView classes that you use like this:

dataTable.WriteListDataContract("SingleRowClassName", @"C:\Path", "ID");

The first parameter is the row class name: the extension will automatically generate the corresponding list class name by appending the "List" string to this class name. The second parameter contains the path of the generated file name (based on the first parameter). The last parameter is an optional string containing a comma seperated list of columns that you want to force as non-nullable (the code will throw an exception when trying to convert a DBNull.Value).

Once you have the generated code files, you can comment out the line.

Using the generated code is very straightforward: just paste it in your WCF source code file. Reuse your old DAL code and, when you have the DataTable or DataView ready, create a list class and call its Load method. The generated code reads in the data and converts it into a generic list that you can immediately return to your Silverlight application.

Here's the source code: DataTableExtensions.cs

Google Maps V3 tip: fitBounds

Never call the fitBounds method on your Google Maps V3 map when the supporting div is hidden. This will result in an incorrectly calculated zoom level because (apparently) the JavaScript code cannot determine the div dimensions. Always make sure the div is visible before calling fitBounds.

A ReadyBoost tip

I own a relatively old laptop (a once-glorious ASUS Lamborghini VX2) which is limited to 2 GB of RAM. The box is now showing its age, especially when using VS 2010. (Not to mention the lack of a WDDM 1.1 driver for the NVidia Ge Force GO 7700, which makes developing for WP7 a horrible experience). To make things run smoother (or at least to try to make them run smoother), I removed all the “Visual experience” checkboxes in VS 2010 (under Tools / Options) and bought an 8 GB USB flash drive for ReadyBoost.
With the standard FAT formatted file system, ReadyBoost is limited to a 4 GB cache. It does make things a little better but barely worth the effort. Recently I read an MSDN article on this subject that stated that this limitation goes up to 32 GB if you format the flash drive using NTFS. After doing so, I got a 7.7 GB ReadyBoost cache (not the full 8 GB because the manufacturers measure capacity in a different but interesting way) and a noticeable improvement for my old box. Now VS 2010 does load a bit faster and the whole thing does feel a bit more agile.
No luck with the NVidia driver, though…

Silverlight 4, FireFox and Accented Characters

My mother gave me a very common portuguese name: João. You can translate it to 'John', 'Jean', 'Juan' (take your pick). The odd thing about my first name are the three consecutive vowels and the tilde character on top of the 'a'. I get all sorts of funny jokes from my anglo-saxon friends due to this personal oddity. Why is this relevant?

I have been working with Silverlight 4 for a web application (I'm essentally rewriting a big HTML SaaS application) and met a very strange behavior with Silverlight 4 when running on FireFox (and Chrome): I just could not write my name on a TextBox! This is a situation that has been reported by some users but, interestingly, it's not a very common complaint. Of course IE works OK with this.

When searching for a solution for this problem, I found a sample where this issue did not happen. After a bit of research I found the culprit: the "windowless" parameter on the HTML object element (my code had it while the sample did not). If you set this parameter to "true", FireFox will not compose the '~' and the 'a' to produce the dreaded 'ã', so beware!

This issue is irrelevant for english-speaking (and writing) users.

Windows Phone Developer Tools Beta

The Windows Phone Developer Tools Beta are now available for download from the Microsoft Download Center.