how to add like button code inside datalist

You need to know the basic about binding your DataList with data. If your questions and answers are stored in your database then you need to query your database and populate your DataList. You can then put an image (like and dislike image) within your DataList and then write the function at the Click event of each Image to store the count of likes/dislikes.

Here's a simple demo on how to bind a DataList with data and to show images:

http://geekswithblogs.net/dotNETvinz/archive/2012/01/11/show-large-image-on-mouseover-with-jquery.aspx