How to register and call Exports in C#

How to call and register Events in C#, with return

        public Exports()
        {
            Exports.Add("Test", new Action<string>(Test));
        }

        private string Test(string content)
        {
            return $"{content} getestet"
        }

CS0407 ‘string Exports.Test(string)’ has the wrong return type

In Lua is it possible

Func should work, instead of Action:

        public Exports()
        {
            Exports.Add("Test", new Func<string, string>(Test));
        }

        private string Test(string content)
        {
            return $"{content} getestet"
        }