The official source of information on Managed Providers, DataSet & Entity Framework from Microsoft
If you upgrade the RTM version of Visual Studio 2008 with the SP1 service pack distribution, the EntityDataSource control does not appear in the Data group of the Web project Toolbox by default. To add the control to the Toolbox:
If you cannot see “EntityDataSource” in the list, you may need to add the assembly manually. To do that, click on the “Browse” button on the “Choose Toolbox Items” window. Then browse for the System.Web.Entity.dll under “C:\Program Files\Reference Assemblies\Microsoft\Framework\v3.5” or the equivalent folder in your configuration.
Diego VegaProgram Manager, ADO.NET