How to prevent Visual Studio Code from opening multiple instances

To prevent Visual Studio Code to open a file in a new Editor, using the following setting. 

Goto File -> Preferences -> Setting

Copy and paste "workbench.editor.revealIfOpen" into search.

Check mark or which sets this setting to true.

In JSON setup file

"workbench.editor.revealIfOpen": true,

The following also must be set to off

"window.openFilesInNewWindow": "off",
"window.openFoldersInNewWindow": "off",