Question

I have a query regarding maintaining a List in between two windows forms. It’s for a project where I need to create an address book.

I have chosen to maintain the contact details in the form of a List. My first windows form (form1) contains a master copy of a list AddressBook, which contains the address book.
I hardcoded 4 entries into the address book list in order to experiment and get the simple functions such as ‘add’ and ‘edit’ working.

I have a second windows form called Add, in which I can add new entries to the list. This works fine. I can add a new contact in the ADD form and this shows up in the initial form1, master form.

My problem arises in the EDIT form. I pass the AddressBook (master) list to the EDIT form. The EDIT form takes the master list and I am able to manipulate the records in that list. However when it comes to sending back the new list to the master page (form1), it does not pick it up. I am using the same code as I do in the ADD form which successfully sends back the new list. However this code does not work when sending back an edited list.

Here is my AddressBook property within form1

public List<Contact> addressBook;
    public List<Contact> AddressBook
    {

       get { return addressBook;} 
       set {addressBook = value;} 

    }

Within EDIT:

public Edit()

    {
        InitializeComponent();           
        temp = Master.AddressBook;    // temp is the temporary List I update within EDIT         

    }

** I then have my algorithm which successfully lets me EDIT the list temp. the list temp now has the edited list**

then when I hit the save button, I use the following code;

Master.AddressBook = temp;

All I need is for the list temp to be sent back to form1.

the code Master.AddressBook = temp; WORKS for when I add values to the list through the ADD form.

ADD FORM:

 public Add()
    {

        InitializeComponent();
        temp = Master.AddressBook;


    }


       **** code to add a new record into the list temp. the new record is called newRecord**********



    private void btnAddClose_Click(object sender, EventArgs e)
    {
        stor.AddressBook = temp; // when I hit close on the form, it updates the master     list AddressBook 
        this.Close(); 
    }

This is all probably very poorly worded but in essence the only bit where my code fails is when I want to change my master Addressbook within form1 by replacing it with the list temp, which is the edited list from my EDIT form.

I think it’s something to do with my AddressBook property. But this doesn’t explain why I can replace AddressBook with a list containing new records but I can’t replace it with a list containing edited records.

Answer 1

One way to accomplish this would be to make the list in Master static.

Master:

    public static List<Contact> AddressBook { get; set; }

Note: You do not need the backing variable, and if you do want to use it, best practices would suggest that it be private. If you do decide to use it, it will also need to be static.

In the Add form, you would then gather the data to create a new Contact object and temp should, in fact, be just a Contact object.
Add Form:

private Contact newRecord = null;
public Add()
{
    InitializeComponent();
    newRecord = new Contact();
}

/**** code to add the user-input to the new Contact object ****/

private void btnAddClose_Click(object sender, EventArgs e)
{
    Master.AddressBook.Add(newRecord);
    this.Close(); 
}

Hope this helps.