I want to use a single app.config by 3 different projects.
How to access the configurations?
ConfigurationManager.AppSettings[\"config1\"]
Let's say you have this folder structure:
Do this:
For each project in Solution Explorer:
Add > Existing Item Select Add as link from the drop down box next to the Add button.
Edited to add:
You correctly state that the above method only shared the file up to build-time. To use a shared file at run-time, see the answers to this question.