Update Listbox when using ObservableCollection

Question

I have an ObservableCollection bound to a listbox like this:

string[] selection = comboEmail.GetItemText(comboEmail.SelectedItem).Split(',');

Employee add = new Employee(Convert.ToInt32(selection[0]), selection[1], selection[2], selection[3]);
displayEmp.Add(add);
listEmail.DataSource = displayEmp;

It adds the data to the listbox(listEmail), however, how do I update it after removal. This is what I've tried so far:

int indexRemoval = listEmail.SelectedIndex;
displayEmp.RemoveAt(indexRemoval);
listEmail.DataSource = displayEmp;
//listEmail.Refresh();

but it doesn't work. How would I update the list after a user as clicked the remove button?

You have some issues with the MVVM way of doing things... Once binded, the ObservableCollection doesn't need to be manually refreshed. Your button should be binded to a Command as well, and the deletion should be using `listEmail.SelectedItem`. Moreover, the binding should take place in the XAML, not the code-behind (which I have no experience with, so I can't help you there). The idea is to let the logic completely out of the UI. — Kilazur, Jun 11 '15 at 14:13
@Kilazur - Thanks, I stick to using regular List<> collection. — Edward Snowden, Jun 11 '15 at 14:18
I have no experience with ObservableCollection, it was suggested to me in another post. I was using List<> collection before, and it was working. I'll stick with it. Any reason, other than more lines of code, why I shouldn't use List<>? — Edward Snowden, Jun 11 '15 at 14:21
You're coming from Winforms, right? I've been there, it's a pretty complicated step to go to MVVM WPF. If you need something that works quickly, suit yourself and use a List; but eventually, if you want to keep on using WPF, you should learn MVVM, bindings and such. As for the reasons, it's not just about a single list, it's about everything you'll use in your program. If it's short, don't bother with MVVM; if you need something maintenable in the future, it's MVVM. — Kilazur, Jun 11 '15 at 14:23
@Kilazur - I shall learn it in good time. Right now I'm building a Winform application, and List<> does the job I need it to do. — Edward Snowden, Jun 11 '15 at 14:25
oh, damn me, I saw ObservableCollection and assumed WPF, my bad. — Kilazur, Jun 11 '15 at 14:26

rageit · Answer 1 · 2015-06-11T14:50:41.857

0

You need to set the ItemSource instead of the DataSource. This assumes that you have also set the DataContext.

listEmail.ItemSource = displayEmp;

Since you have defined your displayEmp as ObservableCollection, your updates should reflect automatically.

EDIT: Here is a sample for your reference using BindingList which auto refreshes the UI:

public BindingList<Data> DataList { get; set; }

public void Load()
{
    DataList = new BindingList<Data>
                   {
                        new Data
                            {
                                Key = "Key1",
                                Value = "Value1"
                            },
                        new Data
                            {
                                Key = "Key2",
                                Value = "Value2"
                            },
                        new Data
                            {
                                Key = "Key3",
                                Value = "Value3"
                            }
                    };
     listBox1.DataSource = DataList;
     listBox1.DisplayMember = "Value";
     listBox1.ValueMember = "Key";
}

public class Data
{
     public string Key { get; set; }
     public string Value { get; set; }
}   

private void button1_Click(object sender, EventArgs e)
{
    DataList.RemoveAt(1);
}

edited Jun 11 '15 at 14:50

answered Jun 11 '15 at 14:24

rageit

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How do I properly remove an item? Could you please update your code to show how to do the removal? – Edward Snowden Jun 11 '15 at 14:26
I'm building a WinForm application, and ItemSource isn't available to me under ListBox. – Edward Snowden Jun 11 '15 at 14:29
ItemsSource is WPF only, it seems. [Try with a BindingList](http://stackoverflow.com/questions/17615069/how-to-refresh-datasource-of-a-listbox-in-c-sharp-winforms). (edit: you see how much of a pain Winforms is ;p) – Kilazur Jun 11 '15 at 14:33
@Kilazur - Thanks for the suggestions, and link :D – Edward Snowden Jun 11 '15 at 14:35
Since you mentioned ObservableCollection I thought you were working with WPF. Like @Kilazur mentioned BindingList works pretty for you. – rageit Jun 11 '15 at 14:42

Update Listbox when using ObservableCollection

1 Answers1