How do I set the properties of a newly added combobox item?

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I can add a series of items to a comboBox as follows:-

foreach (DataRow row in Variables.ClientsTable.Rows)
{
    string temp1 = row["CompanyName"].ToString();
    string temp2 = row["CompanyID"].ToString();
    comboBoxProjects20.Items.Add(temp1);
    comboBoxProjects20a.Items.Add(temp2);
}

However the comboBox then drops down a blank list, which looks to be of the right length. I assume I need to set the DisplayMember and other properties, but how do I select the just added item to do this?

What I have tried:

I started by assigning the DataTable to the comboBox as a datasource. However I have a number of comboboxes all using this same data and I found that changing one changes them all.
I then tried copying the table into a set of Lists to be used, one for each comboBox. Same problem as I have now, so I tried binding Source.
Same problem.
I'm now at the stage of simply adding the items "manually" from the table to keep things simple.

Posted 12-Jan-22 15:06pm

ormonds

Updated 13-Jan-22 10:16am

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2 solutions

Solution 1

you must reset the binding after you add new items at run-time. working code example:

ar inrange0 = new List<int>
{
    1, 2, 3, 4, 5, 6, 7, 8
};

comboBox1.DataSource = inrange0;
inrange0.Add(9);
comboBox1.DataSource = null;
comboBox1.DataSource = inrange0;

If you are not using binding: then, all you need to do is add new items:

C#

// since 'inrange0' is a list of Int, cast and 'ToArray required
comboBox1.Items.Clear();

comboBox1.Items.AddRange(inrange0.Cast<object>().ToArray());

// add another item
comboBox1.Items.Add(9);

Posted 12-Jan-22 17:26pm

BillWoodruff

Updated 12-Jan-22 21:51pm

v2

Comments

ormonds 13-Jan-22 2:50am

But if I am not using a DataSource for the comboBox, simply adding Items one by one in a foreach loop, then the DataSource is always null. I've tried Refreshing the comboBox, but the datalist is still blanks.
I assume that having added the comboBox item as per my code I have to add a value for that item's DisplayMember, but can't see how to select that item:
comboBoxProjects20. ?? . DisplayMember = temp1.

BillWoodruff 13-Jan-22 3:49am

see second example added to solution.

ormonds 13-Jan-22 15:59pm

Thank you. That is what I am doing, but then when the comboBox is used it shows a list of blank items. Do I need to add a DisplayMember property to the comboBox and if so how do I do that? If not, any idea why the items aren't showing?

BillWoodruff 14-Jan-22 4:00am

You use DisplayMember and ValueMember ONLY when you use binding. If you ARE using binding: reset them after you add items and reset the DataSource and see if that makes a difference.

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ormonds · Accepted Answer · 2022-01-13T10:16:00

Solution 2

Found it,
[^]
Thanks for your help.

Posted 13-Jan-22 10:16am

ormonds