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C# Combobox Displaying Blank Items

I'm coding a combobox in C# and for some reason the items in the drop down don't have text. When I have selected an item, it is shown in the combo box text field (the drop down list is always blank whenever I click the drop down button). The datasource seems bound properly because the proper values are being returned when I select items, and the size of the drop down list will change depending on how many items the datasource has. Everything looks fine except for the fact that it seems like my drop down is populated with a bunch of empty strings, which it clearly isn't since as soon as an item is selected the proper text will display.
This is the relevant code:
if (list.Count > 0)
{
cboCustomers.DisplayMember = "Name";
cboCustomers.DataSource = list;
cboCustomers.ValueMember = "ID";
cboCustomers.SelectedIndex = 0;
}
I have looked for an answer to this but can't find it anywhere...I'm sure it's something really simple, but I can't figure it out. The closest problem I found had an answer suggested to set the display member before the data source, which clearly didn't work.
The list is populated from a database query. This will run on keyUp, the idea is that the list is populated as the person is typing based on the info given. So if I wrote 'S' I'd get a combobox with a dropdown that had all the clients starting with 'S'.

Given you don't have any anomalies in your binding, you are probably being affected by DrawMode property of your ComboBox, which may be set to OwnerDrawFixed or OwnerDrawVariable. Set it to Normal and things should get better.

as soon as an item is selected the proper text will display.
A foreground color the same as the background color will produce the same results you are seeing.

ComboBox Items Empty but DataSource Full

After binding a list to combobox, its dataSource.Count is 5 but, combobox item count is 0.
how can it be?
I'm used to Web programming and this is in Windows Forms.
So no combo.DataBind(); method exists.
The problem here is, I'm trying to set the selected item programmatically. Since I don't see the combo.Items collection filled, I cannot set the desired item.
Update
A total update is needed I guess:
datasource contains 7 items
when bound to combobox, DisplayMember and ValueMember are appropriately implemented
after databound, through the gui, I can clearly see the 7 items in the combobox
combobox.DataSource.Count = 7 and combobox.Items.Count = 0
So the problem is here; since after databound no items are there in the ItemCollection of combobox; I cannot search for one to match and set the appropriate one.
Here is a image for better understanding (But I'm pretty sure I'm missing sth simple)

After adding ddl.BindingContext = new BindingContext(); before the BindingSource assignment, everything worked fine.

If you'd expand DataSource items in debuger, you'd probably notice that 1st element on list is null. That is why DataSource does not render ComboBox Items. Removing null items from the list should do all the work;

I had the same problem, but in my case it was caused by calling
combobox.Sorted = True
in InitializeComponent. I guess that call initializes Items, which then prevents the assignment to DataSource from updating it (Items).

What exactly is ListView.RetrieveVirtualItem Event - C#

With respect to a Virtual ListView control in a Winforms App, what are ALL the functions of RetrieveVirtualItem event?
Scenario: There is a Dictionary object which acts as my ListView cache. And its items are displayed on the ListView. On click of a column, the cache dictionary is sorted in memory and the ListView is Refresh()ed. The effect on UI, the ListView is sorted well. :)
But I want to understand what the role of RetrieveVirtualItem Event is, which gets triggered on Refresh().
In the RetrieveVirtualItem event handler [ Someone else's code, :( ], following are done:
Based on RetrieveVirtualItemEventArgs.ItemIndex, get the message from Cache
Set RetrieveVirtualItemEventArgs.Item = retreived item above
It appears that what's done in the event handler is important because, if I take it out, ListView cries. What is the significance of this event?
EDIT
Or let me re-phrase the question... My concern is, Why, after Sorting (and RetrieveVirtualItem event handler), the selected item remains at the location where it was before sorting. I.e, If I select item #5 and sort, and if sorting makes this item as the last item, I would prefer the LAST item to be selected after Sort. But in my case 5th item is selected after sort. So what is the default behavior of RetrieveVirtualItem WRT selected item?

A virtual ListView should only call RetreiveVirtualItem for the rows currently visible on the screen.
As you navigate in the ListView, for example, you press the page down key, the ListView will calculate what should now be the index of the top row and will then call RetrieveVirtualItem so that your code can provide the item to use at each row index.
Unless you cache or otherwise store the items you are providing via RetrieveVirtualItem, they will no longer exist once they are scrolled out of the listview.
This is what the Virtual in VirtualListView means - there aren't any real rows, the rows are virtual. That is how it could display a list containing hundreds of thousands of rows - because it will ever only actually contain how ever many rows are visible on screen.
In effect, the ListView is like a window that is moving up and down your internal list of data - the RetreiveVirtualItem method is what it calls to move items into that window as it moves along. It says, hey I just moved to row 15 - give me the item for that row. It will proceed to call RetreiveVirtualItem for each row index which would be visible. If the ListView was 5 rows in height on the screen, you would receive 5 calls to RetrieveVirtualItem - even if the actual data backing the listview had 3000 items. Each time the top row of the ListView changed (because of navigation), you would receive 5 calls to RetrieveVirtualItem (this is not always the case, but it is the right idea - for example, if you scroll down one row, it will simply ask you for the new last row - it will also simply discard the data that was used for the old top row that scrolled out of view).
I guess it might be even easier to explain if we assume the ListView was only one row high on the display (meaning only a single row is ever actually visible on the screen) - as you move the ListView up and down your list of data (i.e. the user navigates the ListView), it would call RetrieveVirtualItem exactly one time every time it moves to a new row.
Hope that helps...
Good Luck

Virtual listviews only deal with indices. So, if the 5th item is selected before the sort, the 5th item will still be selected after the sort. The control itself has no way of knowing that the data that used to be on the 5th row is now on the first row.
You will have to program that for yourself in your sorting method:
remember which items were selected (remember: you can't use SelectedItems property when in virtual mode)
do the sort
find the indices of the previously selected item now live
select those indices
You can see all this in action in ObjectListView -- a wrapper around a standard .NET ListView.

The RetrieveVirtualItem event is only used when the ListView is put into virtual mode. Rather than retaining ListViewItems in the Items collection (as when not in virtual mode), it creates the ListViewItems dynamically, when needed.
If you don't handle the RetrieveVirtualItem event then no ListViewItems will be added to your ListView. I've attached some sample code for a typical method written to handle the event:
//Dynamically returns a ListViewItem with the required properties; in this case, the square of the index.
void listView1_RetrieveVirtualItem(object sender, RetrieveVirtualItemEventArgs e)
{
//Check if cache has been instantiated yet, and if so, whether the item corresponding to the index requested has been added to the cache already
if (myCache != null && e.ItemIndex >= firstItem && e.ItemIndex < firstItem + myCache.Length)
{
//Return cached item for index
e.Item = myCache[e.ItemIndex - firstItem];
}
else
{
//When item not in cache (or cache not available) return a new ListViewItem
int x = e.ItemIndex * e.ItemIndex;
e.Item = new ListViewItem(x.ToString());
}
}
This example is taken from MSDN (http://msdn.microsoft.com/en-us/library/system.windows.forms.listview.virtualmode(v=vs.90).aspx) where further details can be found.

ListBox ScrollIntoView and SelectedItem unreliable

I currently have a list box set up as follows:
.xaml:
<ListBox Name="DetailsList" ItemsSource="{Binding}" LayoutUpdated="DetailsList_LayoutUpdated" />
.xaml.cs:
private ObservableCollection<string> details = new ObservableCollection<string>();
In the window constructor:
DetailsList.DataContext = details;
I had a button that did the following:
details.Add(System.DateTime.Now.ToString("HH:mm:ss ") + someString);
DetailsList.UpdateLayout();
var lastItem = DetailsList.Items[DetailsList.Items.Count - 1];
DetailsList.SelectedItem = lastItem;
DetailsList.ScrollIntoView(lastItem);
That should select the last item in the list and scroll to it, but it only does it around 75% of the time. Instead, it will often select the second last and scroll to that instead.
I tried moving the scroll and selection into a LayoutUpdated event handler, no change.
I tried two separate buttons - one to add, one to select and scroll. If I add one item at a time then scroll, it seems to be slightly more reliable - it works 90% of the time. If I add half a dozen items before scrolling, it almost never works. It will typically select one of the new items, but not the last one.
Am I doing something wrong, or is there a bug with System.Windows.Controls.ListBox?

The problem is that multiple items with the same string value have been added to the list. When setting the SelectedItem property on the ListView it will call the Equals method to find the correct item. It will select the first item for which Equals returns true which is why you're getting the observed behaviour.
You need to add unique strings (e.g. add milliseconds) or wrap them in another class to be able to uniquely identify them.

ListView SelectedIndexChanged Event no Selected Items problem

I have a small C# 3.5 WinForms app I am working on that grabs the event log names from a server into a listview. When one of those items is selected, another listview is populated with the event log entries from the selected event log using the SelectedIndexChanged event by grabbing the text property of the 1st item in the SelectedItems collection as shown below.
string logToGet = listView1.SelectedItems[0].Text;
This works fine the first time, but a second selection of an event log name from the first listview fails. What is happening is the SelectedItems collection that the SelectedIndexChanged event is getting is empty so I get an ArgumentOutOfRangeException.
I am at a loss. Any ideas on what I am doing wrong or a better way to do this?

Yes, the reason is is that when you select another item, the ListView unselects the SelectedItem before selecting the new item, so the count will go from 1 to 0 and then to 1 again. One way to fix it would be to check that the SelectedItems collection contains an item before you try and use it. The way you are doing it is fine, you just need to take this into consideration
eg
if (listView1.SelectedItems.Count == 1)
{
string logToGet = listView1.SelectedItems[0].Text;
}

You should check that the SelectedItems collection has values in it before you try to retrieve values from it.
Something like:
if(listView1.SelectedItems.Count > 0)
//Do your stuff here

When you select a new item, the previous item is unselected first. Wrap your code in a quick check:
if( listView1.SelectedItems.Count > 0)
{
string logToGet = listView1.SelectedItems[0].Text;
}
This will ignore selected items changing to no selected item.

I had this problem and after spending too much time I realized that the problem is because of trying to get listView1.SelectedItems from another thread. It may be useful for others.