AJAX 1.0 and Visual Studio 2008

Visual Studio 2008 allows to built a project targeting a specific framework (2.0, 3.0 and 3.5) this feature is called multi-targeting which is great when we have to maintain an old project, but unfortunately VS2008 doesn’t work by default with web projects that contains AJAX 1.0, the version of the controls(ScriptManager, ScriptManagerProxy, etc)  for AJAX Extensions is 3.0, on this state only the AJAX Control Toolkit v3.0 is supported.

In order to add the AJAX Control Toolkit v.1.0 to the Toolbox and can work with projects that support AJAX 1.0 you must perform the following tasks:

1. Download the AJAX Extensions for ASP.NET from here and install it.
2. Add the controls on System.Web.Extensions.dll to the Toolbox, to do that, right click on AJAXExtensions tab on the Toolbox, choose ‘Choose items’ the Choose Toolbox Items dialog appears, click on Browse and search for the Extensions library usually installed on /ProgramFiles/Microsoft ASP.NET/ASP.NET 2.0 AJAX Extensions, click OK is expected to have to instances of the controls but is not, don’t worry is OK. VS loads the correct version of the extensions according to the configuration of the project.
3. Create a new toolbox tab for AJAX Control Toolkit v1.0 and for version 3.0, download it from CodePlex, compile it and add to the toolbox as in step2.

Is everything is right you must see

and for the toolkit something similar

Unfortunately when you create a web project targeting the .net framework 2.0 the web.config file does not contain everything necessary to develop with AJAX, the sample config file on the install directory of the AJAX Extensions 1.0 must be added manually to the project, with projects on framework 3.5 there is not such problem.