C#

larsp777 wrote:

Then the book is added to a List-control owned by the customer-object so the customer-object remembers what books the customer has borrowed.

This works fine when the program is running. The problem occurs when I try to save the objects to disc and then retrieve them again when the program starts. I have asked for help and googled it but I can´t make it work.

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

List<Bok> BookList = new List<Bok>();
List<Kund> CustomerList = new List<Kund>();
static string dir = @"C:\Bibliotek\";
string path = dir + "Kunder.xml";
string path2 = dir + "Books.xml";
XmlSerializer xs = new XmlSerializer(typeof(List<Kund>));
XmlSerializer xs2 = new XmlSerializer(typeof(List<Bok>));

public void sparaKund() //Save customerlist
       {


           using (Stream s = File.Create(path))
           {
               xs.Serialize(s,CustomerList);
           }

           using (Stream s2 = File.Create(path2))
           {
               xs2.Serialize(s2, BookList);
           }


       }

private void Form1_Load(object sender, EventArgs e) //Load customerlist
       {

           // deserialize to a new list
           if (File.Exists(path))
           {
               using (Stream s = File.OpenRead(path))
               {

                   CustomerList = (List<Kund>)xs.Deserialize(s);
               }
           }

          if (File.Exists(path2))
          {
              using (Stream s2 = File.OpenRead(path2))
              {
                  BookList = (List<Bok>)xs2.Deserialize(s2);
              }
          }

     }

Book:

 [Serializable()]
    public class Bok : ISerializable

  {
        protected int isbn = 0;
        protected string titel = null;
        protected string author;
        protected int price;
        protected String isType = null;
        protected Kund biblioteksKund = null;

        //egenskaper (properties). Används för att förhindra åtkomst till privata variabler.
        public int ISBN
        {
            get
            {
                return isbn;
            }
            set
            {
                isbn = value;
            }
        }

        public string Titel
        {
            get
            {
                return titel;
            }
            set
            {
                titel = value;
            }
        }

        public string Author
        {
            get
            {
                return author;
            }
            set
            {
                author = value;
            }
        }

        public int Price
        {
            get
            {
                return price;
            }
            set
            {
                price = value;
            }
        }

        public String IsType
        {
            get
            {
                return isType;
            }
            set
            {
                isType = value;
            }
        }
        
        public Kund BiblioteksKund
        {
            get
            {
                return biblioteksKund;
            }
            set
            {
                biblioteksKund = value;
            }
        }


        //Konstruktor (constructor) Metod som körs när objektet skapas. Denna körs om det inte finns parametrar.
        public Bok() 
        {
        }

        //Konstruktor med parametrar
        public Bok(int isbn, string titel, string author, int price, SerializationInfo info, StreamingContext ctxt)
        {
            ISBN = isbn;
            Author = author;
            Titel = titel;
            Price = price;
            biblioteksKund = new Kund();
            this.isbn = (int)info.GetValue("ISBN", typeof(int));
            this.author = (string)info.GetValue("Author", typeof(string));
            this.titel = (string)info.GetValue("Titel", typeof(string));
            this.price = (int)info.GetValue("Price", typeof(int));
            this.biblioteksKund = (Kund)info.GetValue("Kund", typeof(Kund));
         }

        public void GetObjectData(SerializationInfo info, StreamingContext ctxt)
        {
            info.AddValue("ISBN", this.isbn);
            info.AddValue("Author", this.author);
            info.AddValue("Titel", this.titel);
            info.AddValue("Price", this.price);
            info.AddValue("BiblioteksKund", this.biblioteksKund);
        }
 

        //Metod som skriver ut våra variabler.
        public virtual void skrivUt()
        {
            Console.WriteLine("Författare: {0}", Author);
            Console.WriteLine("Titel: {0}", Titel);
            Console.WriteLine("Pris: {0}", Price);
        }

       public virtual String getInfo()
        {
           return null;
        }

        public String getStatus()
        {
            if (BiblioteksKund != null)
                return ("Utlånad till: " + BiblioteksKund.Name);
            else
                return ("Ej utlånad");
        }
    }
}

Customer:

[Serializable()]
    public class Kund : ISerializable

    {
        private int personNr = 0;
        private string name;
        private List<Bok> loan = new List<Bok>(); 
            


        //egenskaper (properties). Används för att förhindra åtkomst till privata variabler.
        public int PersonNr
        {
            get
            {
                return personNr;
            }
            set
            {
                personNr = value;
            }
        }

        public string Name
        {
            get
            {
                return name;
            }
            set
             {
                name = value;
            }
        }

        public List<Bok> Loan
        {
              get
            {
                return loan;
            }

           // set
            //{
             //  loan = value;
            //}
       }

       

        //Konstruktor (constructor) Metod som körs när objektet skapas. Denna körs om det inte finns parametrar.
        public Kund()
        {
        }

        //Konstruktor med parametrar
        public Kund(int personNr, string name)
        {
            PersonNr = personNr;
            Name = name;
           
        }

        public Kund(SerializationInfo info, StreamingContext ctxt)
        {
            this.personNr = (int)info.GetValue("PersonNr", typeof(int));
            this.name = (string)info.GetValue("Name", typeof(string));
        }

        public void GetObjectData(SerializationInfo info, StreamingContext ctxt)
        {
            info.AddValue("PersonNr", this.personNr);
            info.AddValue("Name", this.name);
        }
 
        //Metod som skriver ut våra variabler.
        public virtual void skrivUt()
        {
            Console.WriteLine("Personnr: {0}", PersonNr);
            Console.WriteLine("Namn: {0}", Name);
        }
    }

larsp777 wrote:

It's not a Commercial application.

larsp777 wrote:

Well, you set the unique number when you register a book (Bok) or a customer (kund).

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

larsp777 wrote:

The reason I mentioned that it is not a Commercial application was that I could made sure that no two objects are the same. But maybe that doesn't matter. Shold I use something like a GUID?

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

Eddy Vluggen wrote:

dunno, and this is the place where things get complicated.
 
Let's
say I borrowed Pratchetts' book "Small Gods". You have three books of this story
- how are you gonna track each book you lent?
 
Answer; give every
book a unique number (yeah, like a GUID)

private void btnRegister_Click(object sender, EventArgs e)
        {
             Kund lender = null;
             Bok bookToLend = null;
                                     
            //Search for chosen customer
            foreach (Kund K in CustomerList)
            {
                //Om rätt kund hittas
                if (txtPersonNr.Text.Equals(K.PersonNr.ToString()))
                    lender = K; //Kunden som hittats läggs i ny variabel.
            }
            
            //If customer wasn't found.
            if (lender == null)
            {
                textBox7.Text = "Kund saknas!";
                return;
            }

            //Search for chosen book.
            foreach (Bok B in BookList)
            {
                //Om rätt bok hittas
                if (textBox6.Text.Equals(B.ISBN.ToString()))
                    bookToLend = B;
            }

            //if book wasn´t found.
            if (bookToLend == null)
            {
                textBox7.Text = "Bok saknas!";
                return;
            }

                                 

            if (bookToLend.BiblioteksKund == null) //If book doesn´t have its customer object set.
            {
                bookToLend.BiblioteksKund = lender; //Sets the customerobject of the book.

                lender.Loan.Add(bookToLend);    //Places the book to lend in the customers booklist.

                textBox7.Text = "Lån registrerat!";
            }

           


            
        }

larsp777 wrote:

Or could it be that the list I am trying to save is a empty list even if I use the same name?

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

Eddy Vluggen wrote:

Again, I'd recommend not saving a list of books, but numbers that are linked to
a book.

larsp777 wrote:

But I still have to save the objects somehow so I'm not really sure how that solves anything. Please explain.

CREATE TABLE Customer
(
  Id INT IDENTITY(1,1)
  PRIMARY KEY (Id)
)

CREATE TABLE Book
(
  Id INT IDENTITY(1,1)
  PRIMARY KEY (Id)
)

CREATE TABLE LentItems
(
  CustomerId  INT,
  BookId INT
  FOREIGN KEY (CustomerId) REFERENCES Book(Id),
  FOREIGN KEY (BookId) REFERENCES Book(Id)
)

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

Eddy Vluggen wrote:

Right now, each book would be stored in a Kund? That means that you'd be
"moving" the book-data when the book moves between different Kunds; it'd be
saved in a different list.

larsp777 wrote:

Again, this was a project I made in Java for a University-course a while back. Been trying to transfer it to C#.

Every book (Bok in Swedish) has a reference to the customer who borrowed the book, so it "knows" who borrowed it. The savingpart worked fine in Java but maybe works differently in C#.

Bastard Programmer from Hell
If you can't read my code, try converting it here[^]

Eddy Vluggen wrote:

Those references are pointers; I don't think that the XmlSerializer is going to
save the private loan-list on it's own.