Right-click the Toolbox and select (name it "AJAX Toolkit"). Right-click inside the new tab and select Choose Items .
: This is the modern standard for adding the toolkit to Visual Studio projects. You can install it via the Package Manager Console: Install-Package AjaxControlToolkit Download Ajax Control Toolkit zip
: Remember that most toolkit controls require a ScriptManager or ToolkitScriptManager on the page to function correctly. Right-click the Toolbox and select (name it "AJAX Toolkit")