Answer by Just code for Read a Resourse file using Assembly GetManifestResourceStream method using C#

Try this:

var resourceName = "SingleSignOn.idsrv3test.pfx";using (var stream = Assembly.GetExecutingAssembly().GetManifestResourceStream(resourceName)){  TextReader tr = new StreamReader(stream);  string fileContents = tr.ReadToEnd();}

Note: Put the file as an embedded resource. file > right click > properties > build action > select embedded resource.