How to load data on drop down scroll load ?? (ASP.NET MVC)

Question

Note : I don't want to use jquery Autocomplete. because all available options are not available at a glance.

I have a requirement to create a drop down list which will be empty while loading the page. When the user clicks on the drop down, I want to load the first 20 records (List of names or departments etc) from the SQL Server database using jQuery or javascript and json. When the user scroll down to the last, we have to retain the first 20 records and load the next 20 records from the database.