The ScriptManager control is a core control that performs a key role in implementing the ASP.NET AJAX functionality. It helps to use JavaScript for the Microsoft AJAX Library. It should be noted that AJAX Library on a Web page can only be used if the Web page contains the ScriptManager control. This control makes use of theScriptManager class to maintain the AJAX script libraries and script files. It allows for partial page rendering, Web service calls, and use of ASP.NET AJAX Client Library by rendering the AJAX Library scripts to the browser.

You can find out that an AJAX request has been completed by using the readyState property. If the value of this property equals to four, it means that the request has been completed and the data is available.

No, it is not possible.

The following controls are introduced with the new version of AJAX Control Toolkit:
• SeaDragonExtender control - Refers to the control that is used to deeply zoom the images. You can zoom in or out the image or the particular portion of the image by using the mouse. You can also create a menu over the Seadragon control. This control is helpful when you want to analyze the image closely.
• AsyncFileUploadExtender control - Refers to the control that provides the facility to upload and save the files on the server asynchronously. You can check the outcome either at the server or client side.

ASP.NET AJAX Framework provides a platform where developers can develop such type of applications that use the AJAX concept. The AJAX provides the collection of technologies to create dynamic pages at the client side. The JavaScript requests are responsible to retrieve data from the server or send data to the server. Even some processing at server also requires handling requests, such as searching and storing of data. These tasks are achieved more easily using the AJAX Framework.

AJAX Framework is completely devoted to process requests. The objective of the AJAX engine is to reduce the delays that the user notices while performing a postback to the server. AJAX Framework allows JavaScript functions to send requests to server at the client side. On the other side, it allows the server to process the client's request, searches data, and responds the result to the browser.