Add ONLY checked items from a checklistbox to a listView control

Question

My situation:

I have a populated checklistbox control on Form1. Then I have a listView control on Form2.

I would like for the user to be able to check items on the checklistbox on Form1, then click on a button on Form1 to open Form2.

Form2 contains the listView control, that I want to populate with only the checked items from checklistbox on Form1.

I tried

namespace Boodschappenlijst
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

    public static string[] strKruideniersw = new string[] { Boodschappenlijst.producten[0], Boodschappenlijst.producten[1], Boodschappenlijst.producten[2] };
    public static string[] strVerswaren = new string[] { Boodschappenlijst.producten[3], Boodschappenlijst.producten[4], Boodschappenlijst.producten[5] };
    public static string[] strVerzorgingspr = new string[] { Boodschappenlijst.producten[6], Boodschappenlijst.producten[7], Boodschappenlijst.producten[8], Boodschappenlijst.producten[9] };

    public static List<string> kruidenierswList = new List<string>(strKruideniersw);
    public static List<string> verswarenList = new List<string>(strVerswaren);
    public static List<string> verzproductenList = new List<string>(strVerzorgingspr);

    public static string[] strKruidenierswCh;

    public void Form1_Load(object sender, EventArgs e)
    {
        clbKruidenierswaren.Items.AddRange(strKruideniersw);
        clbVerswaren.Items.AddRange(strVerswaren);
        clbVerzproducten.Items.AddRange(strVerzorgingspr);
        strKruidenierswCh = clbKruidenierswaren.CheckedItems;
    }

    // TODO
    // public string kruidenierswChecked = clbKruidenierswaren.CheckedItems;


    private void button1_Click(object sender, EventArgs e)
    {
        // Create a new instance of the Form2 class
        Form2 form2 = new Form2();

        // Show the settings form
        form2.Show();
    }
}

public abstract class Boodschappenlijst : Form1
{
    public static string[] producten = new string[] { "Peper", "Zout", "Kruidnagel", "Sla", "Komkommer", "Tomaten", "Tandpasta", "Shampoo", "Wax", "Deodorant" };

    // Not working.. clbKruidenierswaren is not static.
    List<string> items = clbKruidenierswaren.CheckedItems.Cast<string>().ToList();

    // Make form1 controls accessible for other classes?
    // Form1 form1 = Application.OpenForms.OfType<Form1>().FirstOrDefault();



}
}

but the I get the error

A field initializer cannot reference the non-static field, method, or property 'Form1.clbKruidenierswaren'.

Can you please direct me to a solution that works?

Answer 1

The problem is you're passing UI objects around, you should be passing data around instead. Here's an example of a Form that can be given data during construction.

public class BaseForm : Form
{
    public object InitialisationData { get; set; }
}

public partial class MagicForm : BaseForm
{
    public string MyBindableGuy;

    public MagicForm()
    {
        InitializeComponent();

        MyBindableGuy = InitialisationData as string;
    }
}

and open it with:

var myForm = new MagicForm();
myForm.InitialisationData = "Hi, I'm a string.";
myForm.Show();

Answer 2

You should make a constructor in the class like this:

Class itself:

public class Boodschappenlijst
{
    public static string[] producten { get; set; } = new string[] { "Peper", "Zout", "Kruidnagel", "Sla", "Komkommer", "Tomaten", "Tandpasta", "Shampoo", "Wax", "Deodorant" };
    private List<string> Items { get; set; }

    public Boodschappenlijst(List<string> items)// << Constructor
    {
        Items = items;
    }
}

And then make an instance the class like so:

On the place (Form?) you have clbKruidenierswaren:

Boodschappenlijst boodschappenLijst = 
           new Boodschappenlijst(clbKruidenierswaren.CheckedItems.Cast<string>().ToList());

Answer 3

public partial class Form1 : Form
{
    // Todo declare the variables
    private List<string> kruidenierswList;
    private List<string> verswarenList;
    private List<string> verzproductenList;

    public Form1()
    {
        InitializeComponent();

        // call the instance once and add that to the variable lijst
        Boodschappenlijst lijst = Boodschappenlijst.Instance; // <- @ others on S/O this is just used as information I know I could do a new as well.

        // initialize the variables
        kruidenierswList = new List<string>() { lijst.Products[0], lijst.Products[1], lijst.Products[2] };
        verswarenList = new List<string>() { lijst.Products[3], lijst.Products[4], lijst.Products[5] };
        verzproductenList = new List<string>() { lijst.Products[6], lijst.Products[7], lijst.Products[8], lijst.Products[9] };
    }

    public void Form1_Load(object sender, EventArgs e)
    {
        // populate the checklist boxes
        clbKruidenierswaren.Items.AddRange(kruidenierswList.ToArray());
        clbVerswaren.Items.AddRange(verswarenList.ToArray());
        clbVerzproducten.Items.AddRange(verzproductenList.ToArray());
    }

    private void button1_Click(object sender, EventArgs e)
    {
        // Create a new instance of the Form2 class
        Form2 form2 = new Form2();

        // Show the settings form
        form2.Show();
    }
}

public class Boodschappenlijst
{
    private static Boodschappenlijst instance;

    public string[] Products
    {
        get;
        private set;
    }

    private Boodschappenlijst()
    {
        Products = new string[] { "Peper", "Zout", "Kruidnagel", "Sla", "Komkommer", "Tomaten", "Tandpasta", "Shampoo", "Wax", "Deodorant" };
    }

    public static Boodschappenlijst Instance
    {
        get
        {
            // singleton initialization => look for design pattern - singleton  <- Design patterns can brighten your day.
            // 
            return instance == null ? instance = new Boodschappenlijst() : instance;
        }
    }
}