C# databound ComboBox changing data in other controls

Question

Once again I have a very complicated question so I'll try and explain as well as I can:

I have a C# Windows Forms (.NET 4) program. My Windows Form contains one large blank panel.
Inside this program, I have a Windows Form UserControl class with a designer. The user control is a box with two ComboBoxes and a TextBox on it (call it a menu choice).

Each ComboBox on the user control is bound to a different DataSource using:

comboBoxSelection1.DataSource = SelectionList1;
comboBoxSelection2.DataSource = SelectionList2;

When the user selects an item using the ComboBoxes, the TextBox shows their choices.
E.g. Selection 1: Steak, Selection 2: Chips.

The entire point of this program is to allow the user to create multiple user controls (menu choices) each with different selections, resulting in a list of selections (which becomes one single order).

With me so far?
This worked absolutely fine before I started using DataSource for the ComboBoxes, like so:

object[] comboBoxList1 = new object[SelectionList1.Count];
int i = 0;
foreach (Selection s in SelectionList1)
{
    string description = s.Description;
    comboBoxList1[i] = description;
    i++;
}
comboBoxSelection1.Items.AddRange(comboBoxList1);

However, I need to use a DataSource in order to differentiate items by id (some displayed names are identical - I cannot change this).

I am now using the following:

comboBoxSelection1.DataSource = SelectionList1;
comboBoxSelection1.ValueMember = "Code";
comboBoxSelection1.DisplayMember = "Name";

The problem is that whenever I change comboBoxSelection1 on one of my user controls, the comboBoxSelection1 value on every user control on the panel changes to my current selection. The same happens with comboBoxSelection2 if I change a value in any comboBoxSelection2, all comboBoxSelection2 boxes change to the same value.

Is this a bug with using one DataSource for multiple controls?
It has been seen here: Data Bound ComboBox: List item changed when I select another

In this case, the issue was solved by using DataBindings rather than DataSource.
As seen here: ComboBox SelectedItem vs SelectedValue.

But when I tried this code my ComboBox item list remained empty:

BindingSource comboBoxSelection1Binding = new BindingSource();
comboBoxSelection1.DataSource = SelectionList1;
comboBoxRuleCustomerGroup.DataBindings.Add("SelectedValue", comboBoxSelection1, "Name", true, DataSourceUpdateMode.OnPropertyChanged);

Any ideas?
Sorry for the overly complex issue, I keep having to write overly complex programs!

score 5 · Accepted Answer · edited May 23 '17 at 11:55

Did a more detailed search after thinking about this in depth over the weekend. My issue in searching before was not knowing really what was happening. I realise now that this is a problem when trying to bind multiple combo boxes to the same dataset.

Finally found this: Multiple ComboBox controls from the same Dataset

The answer is to add the line:

comboBoxSelection1.BindingContext = new BindingContext();

All credit to Blind Fury/John Saunders and Bytes.com.

score 1 · Answer 2 · answered Oct 24 '14 at 19:51

1

You could try refactoring the code snippet starting with object[] to its own method passing in the ComboBox control and SelectionList.

private void PopulateList(ComboBox boxToPopulate, List<String> selectionList)
{
    object[] comboBoxList1 = new object[selectionList.Count];
    int i = 0;
    foreach (Selection s in selectionList)
    {
        string description = s.Description;
        comboBoxList1[i] = description;
        i++;
    }
    boxToPopulate.Items.AddRange(comboBoxList1);
}

Using this method you could have an unlimited number of ComboBoxes and uniquely fill them.

answered Oct 24 '14 at 19:51

Dusty Klingler

11
1

Thank you for the idea, however the reason I've had to switch to data binding rather than adding the descriptions to the combo box individually is that some of the descriptions are identical but have different IDs. Unfortunately this is a list that is completely out of my control and these duplicate names are inevitable (I used the food menu only as an example, my working dataset is much more complicated) The description selected in the combo box needs to be bound to the unique id of the item selected. This is unfortunately why I really need to be using data binding. – Anya Hope Oct 27 '14 at 08:42

score 1 · Answer 3 · answered Oct 22 '15 at 10:07

If you want to totally avoid using Datasource

You could add the items as a class instead fx

ComboBox1.Items.Add(new MyClass("Name", 1))

And then have the class

public class MyClass
    {
        private readonly string _Navn;
        public MyClass(string name, Int id)
        {
            Id = id;
            Name = name;
        }
        public int Id{ get; }
        public override string ToString()
        {
            return Name;
        }
    }

Then when you need the acces the id you do like so.

(ComboBox1.SelectedItem as MyClass).Id

C# databound ComboBox changing data in other controls

3 Answers3