Binding Combobox Using Dictionary as the Datasource

Question

I'm using .NET 2.0 and I'm trying to bind a combobox's Datasource to a sorted dictionary.

So the error I'm getting is "DataMember property 'Key' cannot be found on the Datasource".

        SortedDictionary<string, int> userCache = UserCache.getSortedUserValueCache();
        userListComboBox.DataSource = new BindingSource(userCache, "Key"); //This line is causing the error
        userListComboBox.DisplayMember = "Key";
        userListComboBox.ValueMember = "Value";

score 143 · Accepted Answer · answered Jun 20 '11 at 14:35

143

SortedDictionary<string, int> userCache = new SortedDictionary<string, int>
{
  {"a", 1},
  {"b", 2},
  {"c", 3}
};
comboBox1.DataSource = new BindingSource(userCache, null);
comboBox1.DisplayMember = "Key";
comboBox1.ValueMember = "Value";

But why are you setting the ValueMember to "Value", shouldn't it be bound to "Key" (and DisplayMember to "Value" as well)?

answered Jun 20 '11 at 14:35

Sorin Comanescu

4,581
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Well it shouldn't matter either way. But it might make more sense to switch the two around. However the problem I'm having is with "comboBox1.DataSource = new BindingSource(userCache, null);" I can't pull null there because it gives me an error. – user803952 Jun 20 '11 at 14:42
1

"ArgumentException: Cannot bind to the new display member. Parameter name: newDisplayMember." I don't know what error user803952 got, but this is the error *I* got when I tried doing this with an `IDictionary`. – Ryan Lundy Oct 23 '11 at 04:02
This answer worked for me when I tried to bind a Dictionary to a combobox and received the exception "Complex DataBinding accepts as a data source either an IList or an IListSource." – kad81 May 31 '13 at 04:51
I had no problem using comboBox1.DataSource = new BindingSource(userCache, null); if you think that it is the offending statement, you can try replacing it with : comboBox1.DataSource = userCache.Select(kv => new { Key = kv.Key, Value = kv.Value }).ToArray(); – dmihailescu Jan 07 '15 at 20:06
3

another thing you might want to try is to move the line comboBox1.DataSource = new BindingSource(userCache, null); down after you set the DisplayMember and ValueMember – dmihailescu Jan 07 '15 at 21:01
@SorinComanescu please I just want to know and wish you update your answer of how can we read data back from database to `combobox` that is use dictionary – sam Sep 24 '18 at 19:56
2

Sometimes, if DataSource were assigned before DisplayMember did, execution blocks at DisplayMember assignment line. To me, this works -- cBox.DataSource = null; cBox.DisplayMember = "Value"; cBox.ValueMember = "Key"; cBox.DataSource = new BindingSource(dict, null); // @dmihailescu is right – Park JongBum Aug 12 '19 at 00:45

CristisS · Answer 2 · 2014-06-06T06:38:25.783

23

I used Sorin Comanescu's solution, but hit a problem when trying to get the selected value. My combobox was a toolstrip combobox. I used the "combobox" property, which exposes a normal combobox.

I had a

 Dictionary<Control, string> controls = new Dictionary<Control, string>();

Binding code (Sorin Comanescu's solution - worked like a charm):

 controls.Add(pictureBox1, "Image");
 controls.Add(dgvText, "Text");
 cbFocusedControl.ComboBox.DataSource = new BindingSource(controls, null);
 cbFocusedControl.ComboBox.ValueMember = "Key";
 cbFocusedControl.ComboBox.DisplayMember = "Value";

The problem was that when I tried to get the selected value, I didn't realize how to retrieve it. After several attempts I got this:

 var control = ((KeyValuePair<Control, string>) cbFocusedControl.ComboBox.SelectedItem).Key

Hope it helps someone else!

edited Jun 06 '14 at 06:38

answered Apr 08 '13 at 13:37

CristisS

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This works, i have used the following in my own code to get it to work. https://gist.github.com/psykzz/5374823 – PsyKzz Apr 12 '13 at 20:20
You can also do it like this (getting the selected value): var value = comboBox.SelectedItem; var someItem = value.GetType().GetProperty("Key").GetValue(value, null); – Miroslav Lazovich Jan 14 '14 at 00:10
1

The last line could also be reduced to: var control = ((KeyValuePair) cbFocusedControl.ComboBox.SelectedItem).Key; 1) unnecessary outer parentheses, 2) the compiler knows the Key is a Control already because it is casting to KeyValuePair, so the cast to Control is not needed. – Adam Marshall Jun 04 '14 at 14:32
@AdamMarshall Thanks for the suggestion. Edited the answer per it. – CristisS Jun 06 '14 at 06:39
Instead of all that, why couldn't you just use `cbFocusedControl.ComboBox.SelectedText` and `cbFocusedControl.ComboBox.SelectedValue` to get the DisplayMember and ValueMember respectively? – Sunny Patel Feb 21 '20 at 22:12

score 6 · Answer 3 · answered Oct 08 '14 at 14:28

        var colors = new Dictionary < string, string > ();
        colors["10"] = "Red";

Binding to Combobox

        comboBox1.DataSource = new BindingSource(colors, null);
        comboBox1.DisplayMember = "Value";
        comboBox1.ValueMember = "Key";

Full Source...Dictionary as a Combobox Datasource

Jeryy

score 5 · Answer 4 · answered Mar 20 '14 at 12:19

5

userListComboBox.DataSource = userCache.ToList();
userListComboBox.DisplayMember = "Key";

answered Mar 20 '14 at 12:19

Yelnar

81
1
4

Clean and simple. – hubert17 Jan 21 '19 at 18:09

score 2 · Answer 5 · edited Aug 02 '12 at 08:51

A dictionary cannot be directly used as a data source, you should do more.

SortedDictionary<string, int> userCache =  UserCache.getSortedUserValueCache();
KeyValuePair<string, int> [] ar= new KeyValuePair<string,int>[userCache.Count];
userCache.CopyTo(ar, 0);
comboBox1.DataSource = ar; new BindingSource(ar, "Key"); //This line is causing the error
comboBox1.DisplayMember = "Value";
comboBox1.ValueMember = "Key";

score 1 · Answer 6 · edited May 21 '20 at 22:41

1

I know this is a pretty old topic, but I also had a same problem.

My solution:

how we fill the combobox:

foreach (KeyValuePair<int, string> item in listRegion)
{
    combo.Items.Add(item.Value);
    combo.ValueMember = item.Value.ToString();
    combo.DisplayMember = item.Key.ToString();
    combo.SelectedIndex = 0;
}

and that's how we get inside:

 MessageBox.Show(combo_region.DisplayMember.ToString());

I hope it help someone

edited May 21 '20 at 22:41

Arman Ebrahimpour

3,537
1
9
37

answered May 21 '20 at 12:17

jacek

19
5

It did. Thank you! +upvote – Michael Tucker May 18 '21 at 14:40

score 0 · Answer 7 · edited Jan 07 '15 at 06:03

0

Use -->

comboBox1.DataSource = colors.ToList();

Unless the dictionary is converted to list, combo-box can't recognize its members.

edited Jan 07 '15 at 06:03

th1rdey3

3,888
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answered Jan 07 '15 at 05:38

Swaraj

1

score 0 · Answer 8 · answered Feb 25 '16 at 10:14

Just Try to do like this....

SortedDictionary<string, int> userCache = UserCache.getSortedUserValueCache();

    // Add this code
    if(userCache != null)
    {
        userListComboBox.DataSource = new BindingSource(userCache, null); // Key => null
        userListComboBox.DisplayMember = "Key";
        userListComboBox.ValueMember = "Value";
    }

score 0 · Answer 9 · answered Jun 20 '11 at 14:28

0

If this doesn't work why not simply do a foreach loop over the dictionary adding all the items to the combobox?

foreach(var item in userCache)
{
    userListComboBox.Items.Add(new ListItem(item.Key, item.Value));
}

answered Jun 20 '11 at 14:28

thekip

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Binding and adding items is not the same thing. Well, maybe that's what the OP really needs, who knows? ;) – jv42 Jun 20 '11 at 14:30
I know but I don't see any code that is dependent on the databinding itself. – thekip Jun 20 '11 at 14:31
Well what you suggested would work, but the "new ListItem" exists in the System.Web.UI.WebControls Namespace and I wouldn't import that for a windows form application. – user803952 Jun 20 '11 at 14:38
I wouldn't do that either, I assume there's a winforms equivalent though? I'm not that into winforms. – thekip Jun 20 '11 at 15:32
new ComboBoxItem("itemtext","itemid"); can be used instead – ashveli Oct 15 '19 at 04:41

Binding Combobox Using Dictionary as the Datasource

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