After installing Visual Studio 2008 SP and .NET Framework 3.5 SP1 I tried to create and run a quick dynamic data test site and got at least the following errors –

Error 3 ‘System.Web.DynamicData.FieldTemplateUserControl.Mode’ is not supported by the language C:\Users\matt\Documents\Visual Studio 2008\Projects\DDWebApplication\DDWebApplication\DynamicData\FieldTemplates\ForeignKey_Edit.ascx.cs 37 17 DDWebApplication

Error 5 ‘System.Runtime.Serialization.DataContractAttribute’ does not contain a definition for ‘IsReference’ c:\users\matt\documents\visual studio 2008\projects\ddwebapplication1\ddwebapplication1\model1.designer.cs 286 65 DDWebApplication1

Warning 1 Reference to type ‘System.Web.UI.WebControls.DataBoundControlMode’ claims it is defined in ‘c:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Web.dll’, but it could not be found c:\Program Files\Reference Assemblies\Microsoft\Framework\v3.5\System.Web.DynamicData.dll DDWebApplication1

To cut a very LONG (and brain aching) story short, my installation BELIEVED it had installed correctly with no error messages, BUT it simply had not upgraded .net framework 3.0 and 3.5 to the appropriate SP2 and SP1!!

The only way to fix this (re-installing over the top was no good) was to uninstall (when doing this you will notice that hotfixes et al are not installed in the first place) and reinstall as per this excellent guide from Aaron Stebner (who suggested this in the 1st place) –

If this is not your issue, here ‘some’ are Other links I travelled through in trying to fix this –

Hope this helps save someone some grief!