For AJAX development, the Microsoft AJAX Library package contains the complete set of client JavaScript resources for ASP.NET AJAX client framework components in ASP.NET 3.5. The Microsoft AJAX Library is primarily intended for these scenarios:
Note For ASP.NET users, the Microsoft AJAX Library includes the JavaScript resource files that are available to ASP.NET pages that contain a ScriptManager server control.
The Microsoft AJAX Library package supports the following browsers:
A bug in ASP.NET 3.5 requires that the script files in the Microsoft AJAX Library have the locale suffix in the file name when referenced by the ScriptManager control's ScriptPath property.
In ASP.NET, non-default AJAX script files can be used by specifying the ScriptPath property of the ScriptManager control. The issue is that in some scenarios, the ScriptManager control expects the file names to include the locale suffix. For example, there are scenarios where the ScriptManager control expects the name MicrosoftAjax.en-US.js instead of MicrosoftAjax.js.
The Microsoft AJAX Library 3.5 accounts for this bug and ships duplicate files whose name includes the locale suffix. This means that MicrosoftAjax.en-US.js is identical to MicrosoftAjax.js;. MicrosoftAjaxWebForms.js is identical to MicrosoftAjaxWebForms-en.US.js, and so on for the other framework JavaScript (.js) files in the Microsoft AJAX Library.
In other scenarios, in the Microsoft AJAX Library 3.5 you can continue to use the files without the locale suffixes, as was the case in the Microsoft AJAX Library 1.0.