What your looking for is called: Intellisense
The sole goal of this feature is to allow coding to be more productive, smarter, and easier.
You can renable Intellisense by hitting CTRL + J. That will manually reactivate it. Otherwise you'll need to go to:
- Tools
- Options
- Text Editor
- Auto List Member
But one of those should address your issue. Otherwise I might suggest running a repair on Visual Studio or Restoring it back to defaults. Cause by default it is enabled and configured correctly.
A known issue can also come from third-party Add Ons that actually handle such data can cause issues with Intellisense so uninstalling such Add Ons, then defaulting Visual Studio should fix it as well.
Example:
- Resharp
- Visual Assist X
- Just Code
- Etc.
Basically the ones that handle code completion, quick coding features.
Here is an article from Microsoft Developer Network.
Hopefully that helps.