Restricting a method to Ajax calls only, an example of ActionMehodSelector in Asp.net MVC, If request is an ajax request, it will be served by action method, Else It will not.

AjaxOnlyAttribute.cs

public class AjaxOnlyAttribute : ActionMethodSelectorAttribute
{
public override Boolean IsValidForRequest(
  ControllerContext controllerContext, MethodInfo methodInfo)
  {
    return controllerContext.HttpContext.Request.IsAjaxRequest();
  }
}