How to read existing text files without defining path

You could use Directory.GetCurrentDirectory:

var path = Path.Combine(Directory.GetCurrentDirectory(), "\\fileName.txt");

Which will look for the file fileName.txt in the current directory of the application.

When you provide a path, it can be absolute/rooted, or relative. If you provide a relative path, it will be resolved by taking the working directory of the running process.

Example:

string text = File.ReadAllText("Some\\Path.txt"); // relative path

The above code has the same effect as the following:

string text = File.ReadAllText(
    Path.Combine(Environment.CurrentDirectory, "Some\\Path.txt"));

If you have files that are always going to be in the same location relative to your application, just include a relative path to them, and they should resolve correctly on different computers.

If your application is a web service, Directory.CurrentDirectory doesn't work.

Use System.IO.Path.Combine(System.AppDomain.CurrentDomain.BaseDirectory, "yourFileName.txt")) instead.