ListBox doesn't show changes to DataSource

问题

I thought this was a simple problem, but I can't find any information on the web. I'm binding a ListBox to a List using BindingSource like so:

List<Customer> customers = MyMethodReturningList();

BindingSource customersBindingSource = new BindingSource();
customersBindingSource.DataSource = customers;

customersListBox.DataSource = customersBindingSource;

Now, when I add or delete from customers list, my ListBox gets updated (even without using ResetBindings on BindingSource), but if I change any of the customer objects in the list, it does not. Calling ResetBindings has no effect. I even implemented my own BindingList, but the behaviour hasn't changed.
The Customer class uses properties for accessing and modification of data. Its ToString() content is displayed in the list.

I'm using C# in .Net 2.0.

Any ideas?

Thanks

回答1:

If you use a BindingList you don't even need the BindingSource:

BindingList<Customer> customers = new BindingList<Customer>(MyMethodReturningList());
customersListBox.DataSource = customers;

回答2:

OK, here's a dirty fix: wenever you need to refresh the box contents set datasource = null, then rebind it.

the reason it doesn't update is because the objects in the list haven't changed and it only checks the refrences of the object rather than their contents.

回答3:

There is also a bug in the list box which can cause this problem. If you set the SelectionMode to None this problem appears.

As a work around I set the selection mode to One and then back to None when updating the datasource.

回答4:

I got around this problem by converting data to array when updating source. Please see UpdateData method. This way you can update your combo box without losing ComboBox Settings.

class Person {
   public int Id {get; set; }
   public string FirstName{ get; set; }
   public string SurName {get; set; }
}

public Form1()
{
    InitializeComponent();
    comboBox1.DisplayMember = "FirstName";
    comboBox1.ValueMember = "Id";
    comboBox1.DataSource = m_PersonList;
}

public void UpdateData() {
    m_PersonList[0].FirstName = "Firstname1";
    comboBox1.DataSource = m_PersonList.ToArray<Person>();
}

回答5:

I understand that this question was asked almost 6 years ago but other than work-arounds I do not see a correct answer here. When you change property of an item in a collection the event gets raised for the element (object) but not the collection. So the collection does not see a change and will not refresh bound controls. Elements inside all binding collections and most generic collections like List<> receive 2 events, PropertyChanging and PropertyChanged. When a property of the element inside collection is changed, the event gets triggered. All you need to do is add an event handler that would trigger either re-binding or raise an event on the Collection.

来源：https://stackoverflow.com/questions/1609544/listbox-doesnt-show-changes-to-datasource

标签

data-binding

listbox

c#-2.0