Can I use read-only to automatically implement properties- Is read-only auto-implemented property possible?

problem ：

I found a topic on MSDN that talks that yes, this is possible. I am here MSDN Found a topic on , Yes , It's possible .

I did a test that seems to break this statement: I did a test that seemed to break this statement ：

using System;namespace Test{    class Program    {        static void Main(string[] args)        {            Foo f = new Foo("1");            Console.WriteLine(f.Bar); // prints 1            f.Test("2");            Console.WriteLine(f.Bar);// successfully prints 2        }    }    class Foo    {        public Foo(string b)        {            this.Bar = b;        }        public string Bar { get; private set; }        public void Test(string b)        {            // this would be impossible for readonly field!            // next error would be occur: CS0191 or CS0191            // A readonly field cannot be assigned to (except in a constructor or a variable initializer)            this.Bar = b;         }    }}

Where am I wrong? What's wrong with me ？

---

Solution ：

Reference resources ： https://stackoom.com/en/question/API7