How to get list of contents of a particular content type programattically How can i get a list of contents of a particular content type for example "Basic Page". I want basic page title list in a drop down. 

I want list of nodes in a drop down and while selecting each will show the content body. How can i do this?
To create a list of content with filters (e.g. by type) you probably want to use either Views or, if you have a reason to load whole entities by ID rather than individual fields, an EntityFieldQuery.

Since there may be a large number of nodes, this type of use case usually uses an autocomplete field by entity title rather than a dropdown.

To create a dropdown, you'll want to use the core Form API to create a form, and the #options array for the dropdown field would be provided by either the View or EntityFieldQuery you create.