Step by Step Installation Guide

Visual Studio Extension

To install the ASP.NET AJAX Control Toolkit run the new installer from DevExpress.com:
Accept the License Agreement and the AJAX Control Toolkit will be installed for each supported Microsoft Visual Studio version installed (check the Home page for supported versions list).
After the installation is over, create new ASP.NET Web Forms project in Visual Studio:
To show the AJAX Control Toolkit controls in the Toolbox select any .aspx page in the Solution Explorer:
Once you drag any of the Toolkit controls on the page, an assembly reference is added to the project automatically, and the AJAX Control Toolkit assembly is registered on the page:

Note: TagPrefix is autogenerated field and can be changed according to your needs.

Note: NuGet packages do not provide Toolbox integration

As the dialog window appears select "Online" on the left and type in "Ajax Control" to find the AJAX Control Toolkit package:

Click "Install". After the package is installed an assembly reference will be added to the project automatically:

Open an .aspx page and register assembly for this page:

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>

Note: TagPrefix can be changed according to your needs.

This content was moved from https://ajaxcontroltoolkit.codeplex.com/documentation to this Documentation wiki. This is now the authoritative location of the AJAX Control Toolkit documentation.