How can I copy combobox contents programmatically?

Question

I've got this code:

private void FormMain_Shown(object sender, EventArgs e)
{
    ComboBox cmbx;
    foreach (Control C in this.Controls)
    {
        if (C.GetType() == typeof(ComboBox))
        {
            cmbx = C as ComboBox;
            //cmbx.Items.AddRange(cmbxRow0Element0.Items); <= illegal
            object[] obj = new object[cmbxRow0Element0.Items.Count];
            cmbxRow0Element0.Items.CopyTo(obj, 0);
            cmbx.Items.AddRange(obj);
        }
    }
}

...but it doesn't work - I have several combo boxes on a tabPage on a tabControl on a Form, with cmbxRow0Element0 populated with items at design time. The above attempt to copy its items to all the other comboboxes fails, though.

UPDATE

This is the code I now have, and it still doesn't work:

public FormMain()
{
    InitializeComponent();

    for (int i = 0; i < 10; i++)
    {
        this.cmbxRow0Element0.Items.Add(String.Format("Item {0}", i.ToString()));
    }
    foreach (Control C in this.Controls)
    {
        ComboBox cmbx = null;

        // The & test ensures we're not just finding the source combobox
        if ((C.GetType() == typeof(ComboBox)) & ((C as ComboBox) != this.cmbxRow0Element0))
            cmbx = C as ComboBox;
        if (cmbx != null)
        {
            foreach (Object item in cmbxRow0Element0.Items)
            {
                cmbx.Items.Add(item);
            }
        }

    }
}

Perhaps it's something to do with the comboboxes being on tab pages on the tab control?

UPDATE 2

A breakpoint on the first line below is reached, but the second line is never reached:

if ((C.GetType() == typeof(ComboBox)) & ((C as ComboBox) != this.cmbxRow0Element0))
   cmbx = C as ComboBox;

UPDATE 3

The problem was the "find" was not being specific enough - the particular tabPage has to be specified. For more details, see this.

Selman Genç · Answer 1 · 2014-05-23T00:11:26.617

1

Try this:

var items = cmbxRow0Element0.Items.OfType<object>().ToArray();

foreach (ComboBox c in this.Controls.OfType<ComboBox>())
{
     c.Items.AddRange(items);
}

If you are using tabControl as a container, then it means your comboboxes aren't direct child element of your Form.So you need to access Control collection of the container which is the tabControl. You can do that using this.NameOfYourTabControl.Controls.

edited May 23 '14 at 00:11

answered May 22 '14 at 23:43

Selman Genç

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The other combo boxes are not populated with the values from cmbxRow0Element0. – B. Clay Shannon-B. Crow Raven May 23 '14 at 00:00
@B.ClayShannon instead of this.Controls. can you try using : `this.NameOfYourTABControl.Controls`? – Selman Genç May 23 '14 at 00:02
That also fails (foreach (ComboBox c in this.tabControl1.Controls.OfType())) – B. Clay Shannon-B. Crow Raven May 23 '14 at 15:10

Ken White · Answer 2 · 2014-05-23T16:25:55.460

1

A quick test Windows Form app (VS Express 2012) shows this works. In a new blank Windows Form app, drop three (or more) ComboBox controls:

    public Form1()
    {
        InitializeComponent();
        for (int i = 0; i < 10; i++)
        {
            this.comboBox1.Items.Add(String.Format("Item {0}", i.ToString()));
        }
        foreach (Control C in this.Controls)
        {
            ComboBox cmbx = null;

            // The & test ensures we're not just finding the source combobox
            if ((C.GetType() == typeof(ComboBox)) & ((C as ComboBox) != this.comboBox1))
                cmbx = C as ComboBox;
            if (cmbx != null)
            {
                foreach (Object item in comboBox1.Items)
                {
                    cmbx.Items.Add(item);
                }
            }

        }
    }

edited May 23 '14 at 16:25

answered May 22 '14 at 23:58

Ken White

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I don't want to have to specify each subsequent combobox by name (as "comboBox2" above; there will be dozens of them. – B. Clay Shannon-B. Crow Raven May 23 '14 at 15:12
I don't see any reason you'd have to; if you have a reference to any combobox, you can use that as either the source or destination for the copy using the code here (which is what your question asks). IOW, `cmbx = C as ComboBox; foreach (Object item in srcCombo.Items) { cmbx.Items.Add(item); }` works fine. – Ken White May 23 '14 at 16:00
I'm editing to add a (rather meaningless) example of how you can use it without knowing the name of the destination ComboBox first, just to show it can be done with the logic above. :-) – Ken White May 23 '14 at 16:17
This does not work, either; it appends "Item 0" ... "Item 9" to the original combobox, but does not populate the others. – B. Clay Shannon-B. Crow Raven May 23 '14 at 16:24
Then you're not using the code I posted. I tested it thoroughly, with a new blank Windows Form and three ComboBox controls (as the text says), and each list ended up with a single copy of the numbered list. Would you like me to attach an image to show it? The `& ((C as ComboBox) != this.comboBox1))` specifically eliminates the source combo from being included. – Ken White May 23 '14 at 16:31

How can I copy combobox contents programmatically?

UPDATE

UPDATE 2

UPDATE 3

2 Answers2

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