Code Completion features help you write code faster. While you type, ReSharper analyses surrounding context and symbols your recently entered in order to suggest suitable values gathered in completion list.
To learn more about Symbol Completion, see
Suggesting Variable Names
After a variable is declared, it is included in the completion list and can be suggested by ReSharper.
Suggesting User-Defined Methods
It also can suggest methods defined by you somewhere in your solution.
Suggesting Methods and Properties for DOM Elements
When you're working with DOM elements, ReSharper will include corresponding methods and properties in
the completion list.
Suggesting user-defined properties or standard ones (for example, DHTML properties).