How to read a text file in project's root directory?

From Solution Explorer, right click on myfile.txt and choose "Properties"

From there, set the Build Action to content and Copy to Output Directory to either Copy always or Copy if newer

You can use the following to get the root directory of a website project:

String FilePath;
FilePath = Server.MapPath("/MyWebSite");

Or you can get the base directory like so:

AppDomain.CurrentDomain.BaseDirectory

Add a Resource File to your project (Right Click Project->Properties->Resources). Where it says "strings", you can switch to be "files". Choose "Add Resource" and select your file.

You can now reference your file through the Properties.Resources collection.