C#

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).

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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?

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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?

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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)
)

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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#.

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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.

larsp777 wrote:

No, I don't think I did it in XML. I saved the objects in a binary format.

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