ref var of object inside a method

Question

there is a program of a document manager that pushes the document to a Queue

There are 3 questions on 3 different threads, base on the same program

this is the THIRD question

the program is :-

using System;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
namespace scratchpad3
{
    class Program
    {
        public static void Main()
        {
            var dm = new DocumentManager<Document>(); //************************2
            dm.AddDocument(new Document("Title A", "Sample A"));//**************4
            dm.AddDocument(new Document("Title B", "Sample B"));
            dm.DisplayAllDocuments();
            if (dm.IsDocumentAvailable)
            {
                Document d = dm.GetDocument();
                Console.WriteLine(d.Content);
                Console.Read();
            }
        }
    }
//    >>>>>>>>>>>>>>>>>>>>>>>>> decl of a class
    public class DocumentManager<T>
where T : IDocument			//************************1
    {
        private readonly Queue<T> documentQueue = new Queue<T>();
        public void AddDocument(T doc) //************************3
        {
            lock (this)
            {
                documentQueue.Enqueue(doc);
            }
        }
        public bool IsDocumentAvailable
        {
            get { return documentQueue.Count > 0; }
        }
        public T GetDocument()
        {
            T doc = default(T);
            lock (this)
            {
                doc = documentQueue.Dequeue();
            }
            return doc;
        }
         public void DisplayAllDocuments()
        {
            foreach (T doc in documentQueue)
            {
                Console.WriteLine(doc.Title);
            }
        }
    }
//>>>>>>>>>>>>>>>>>>>>>>>>>>>>> decl of a class
    public interface IDocument
    {
        string Title { get; set; }
        string Content { get; set; }
    }
    public class Document : IDocument
    {
        public Document()
        {
        }
        public Document(string title, string content)
        {
            this.Title = title;
            this.Content = content;
        }
        public string Title { get; set; }
        public string Content { get; set; }       
    }
}

 public void AddDocument(T doc) // //************************3

"T  doc" may create a reference variable to an object called doc

but instead of passing a reference variable we are passing an object in the method call as:-

 dm.AddDocument(new Document("Title A", "Sample A"));//************************4

etc ....

case1)        Why this anomaly?

Answer 1

thwe question did not print well so I give you this way
case1) 	Why this anomaly?
Case2)   Can we intuitively know from a coding where it is a reference variable that is to be passed as a paremeter and where an object is to be passed as a parameter? 

Answer 2

dm.AddDocument(new Document("Title A", "Sample A"))

Here, there is nothing like passing the object to AddDocument function. Whenever you create an object like new Document(...) It always returns a reference to newly created object. In your case that reference is not stored anywhere but it is directly passed to AddDocument.

So, where is the anomaly.. right?

I hope this helps.

---

Please mark this post as answer if it solved your problem. Happy Programming!