Issues with data binding, Typed Datasets, DataRows and Null Values

Had some fun this morning as we’re trying to get a simple framework set up for a web app, that others can understand, using out-of-the-box functionality if possible.  I tried to avoid the normal tendency to put the ‘architecture hat‘ on and overcook it.  If you can’t be bothered to read all of this then just scroll to the bottom for the ‘take home’ on binding against typed datasets with null values.

We started off the prototype with a typed Dataset (including a couple of DB tables, and key relationships between each), a table adapter for each table, and a DetailsView at the front end, bound to an objectdatasource, which in turn talks to a business object that calls the TableAdapter.  That’s a lot for one sentence so from top to bottom…

DetailsView –> ObjectDataSource –> BusinessService –> TableAdapter –> Database

This all sounds pretty straightforward, and it is – unless (as in this case) you decide to have your business object pass back a single (strongly typed) DataRow for your front end to bind against.  This seemed reasonable at the time because I only ever want to show one row here.

You’ll basically get a StrongTypingException for every null field you try and bind, because by default a null field value will raise an exception when accessed through its generated property. 

We got distracted for a while exploring this as the natural tendency is to think ‘ah – I’ll make sure it doesn’t raise the exception’ – treating the symptom rather than the cause.

It turns out that any non-string field in a typed dataset table can’t have a default of null (or anything other than ‘raise exception’).  If you stuff in a _null value directly in the XSD your fields will disappear from the public properties (rather curiously) when you compile – so that’s not an ‘enterprise’ option.

I tried changing the return type in my business method to a generic DataRow to try and force the data binding to NOT use the strongly typed properties (getting warmer but still no dice.  I knew I was missing something really simple…

I then stumbled across a post (bottom of the page) that illustrated databinding will use different methods to bind based on what interfaces it finds.  The binding mechanism basically has no choice but to use the strongly typed public properties on a strongly typed or generic DataRow, as there’s no way for it to successfully enumerate the values.  If you bind against almost anything else you’ll most likely have no issues (it appears the databinding doesn’t rely solely on ITypedList).  We’re now binding against a typed DataTable (rather than generic DataView) and all’s fine.  If you want (rather) more info on ITypedList then look here.


Don’t databind against a typed (or untyped) DataRow!

Setting up a Continuous Integration .NET Build Server without Visual Studio

We start with Windows XP SP2 (doesn’t really need to be a ‘server’).  My requirement is to rely on the .NET framework and open source tools – i.e. not requiring a Visual Studio Licence.  We’re using .NET 2.0 so everything will be in reference to that.

I assume here that you’ll be familiar with the actual software below and just want to get a Build Server up and running without having to install Visual Studio.  If you’re not familiar with Continuous Integration then start by looking at Martin Fowler’s Continuous Integration article and then the info on CruiseControl.NET, as that’s the tool that pulls everything together. 

There’s help on each of the sites below for installing and using each of the tools, so I won’t go into detail about each one.  The order of the list isn’t critical, but you’ll probably have some issues unless all are done.

  1. Install IIS from Add/Remove Windows Components (used for CruiseControl.NET) if not already present
  2. Open up a command prompt and run C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\aspnet_regiis.exe -i (to install ASP.NET in IIS)
  3. Install CruiseControl.NET (1.4) from  NOTE:  If you’re using a remote SubVersion repository (as in my case) then you’ll need to run the CruiseControl.NET Service as a domain user that has access to the network location of the repository  rather than LocalSystem.  This is because CruiseControl will be using the SVN client to poll for changes. 
  4. Install Microsoft .NET Framework 2.0 SP1 from
  5. Install latest SubVersion (1.5) from
  6. Install appropriate NUnit from (targeting .NET framework 2.0 – I have 2.4.6)
  7. Install latest FxCop from
  8. Install .NET Framework 2.0 SDK from (you’ll need this to get around a NAnt bug whereby it can’t resolve an internal property to load the .NET framework)
  9. Download latest NAnt from
  10. Download latest NAntContrib from (You’ll need this to run MSBuild)
  11. To save getting errors when building Web Projects (and other types) the easiest thing is to copy c:\program files\msbuild from your dev machine to the build server (otherwise you’ll have to alter the path of where the targets are in each project).

Once you’ve got all of these set up then you’ll be able to add some builds to your ccnet.config file ( most likely c:\program files\CruiseControl.NET\server\ccnet.config)

Test CruiseControl’s happy by going to http://localhost/ccnet It should come up OK but basically show ‘no projects’.

I’m not going to go into detail about setting up the builds here but may cover that in a follow up article, as it requires some more setup with SVN and a ‘standard’ project structure (to get benefit from reuse of build scripts).  If you’re still with me then I’ll share one last thing which might help… 

Some people choose to have NAnt in a standard place and just reference it from the PATH, but I now use the power of svn:externals to drag in NAnt, NUnit and other common external dependencies like MS Enterprise Library from a shared SVN location to each project.  This means you just get latest of a project and it has ‘everything’ needed to build – no installations or assumptions about locations of tools.