How to Install AJAX Control Toolkit in Visual Studio:
In this article I'm trying to explain from where we can download AjaxToolkit.dll and how to Install AjaxControlToolkit into our project and how to add those controls into our solution Toolbox.
Follow below steps to achieve your goal.
Download AjaxControlToolkit using below link "http://ajaxcontroltoolkit.codeplex.com/" and then choose Download option there it will display the supported files with versions. Choose your visual studio version and download the toolkit as per your version. Here, 3 versions of Toolkit will be available Ajax Control Toolkit .NET 3.5, Ajax Control Toolkit .NET 4.0, Ajax Control Toolkit .NET 4.5. Choose your framework and download appropriate toolkit for that.
After download the required version of Toolkit then add the available controls into our Solution Toolbox. Right click on Toolbox and choose "Add Tab" option and then give a name for that as "AjaxControlToolkit".
After create a Tab under Toolbox then add Ajax Controls into that tab by right click on the tab and then choose “Choose Items” option then choose your downloaded file and then add “AjaxControlToolkit.dll” to that solution. Then it will display the list of controls available under that. Then choose the controls whatever you required and then click on “Ok” button then automatically controls to be added to that tab.
After adding Items to the Toolbox the controls become like below.
Now, you can use the controls, whatever you want to implement your task. Hope this article will help you to install the AjaxToolkit into your solution.