I got a problem with a ListBox in a WinForm application. I have two ListBoxes inside of a tab control and depending on the selection in the first one (lb1), the DataSource of the second one (lb2) changes. This is done in the SelectedValueChanged Event.
private void listBox_ControlUnits_SelectedValueChanged(object sender, EventArgs e)
{
ControlUnit unit = (sender as ListBox).SelectedItem as ControlUnit;
textBox_ProjectNameTab.Text = unit.ProjectName;
listBox_ControlCircuits.DataSource = null;
listBox_ControlCircuits.DataSource = unit.ControlCircuits;
}
lb1 is filled with a DataSource, too.
Now if I select a value in lb1 the selection automatically jumps back to the first item and I can not figure out why. is this some kind of UI update problem?
Even without the SelectedValueChanged event and the connection to the second listbox the issue occures.
Short gif of the problem, sorry for the blurriness
If I select one item more than once it works somehow (as seen in the gif).
Edit:
I found the problem but I do not quite understand what happens.
I have another listBox on another tab of my tab control. This listBox has the same DataSource as lb1. This seems to cause this behavior.
I finally found the problem:
I did not know that if I use the same DataSource for two ListBoxes they share the BindingContext per default.
I created a new BindingContext for the second ListBox and now the selection does no longer change.
listBox_allGroups.DataSource = null;
listBox_allGroups.DataSource = x.y;
listBox_allGroups.DisplayMember = "Name";
listBox_ControlUnits.DataSource = null;
listBox_ControlUnits.DataSource = x.y;
listBox_ControlUnits.DisplayMember = "Name";
listBox_ControlUnits.BindingContext = new BindingContext();
You can use a variable to hold the selected item
object _selecteditem=null;
and check it in ListBox click event.
prive void ListBox1_Click(object sender,EventArgs e)
{
if(ListBox1.SelectItem == _selecteditem) return;
// do ...
}
I have five ComboBoxs which are using the same enum content.
Each ComboBox should not have the same value.
If box one has selected content "beef", box two has selected the content "beer".
And now I select "beer" in box one, and both contents should switch. I'm actually using a method with checks both with if and else (working, but really boring).
Is there a smarter solution?
For each box I have one of this trigger and Model.BoxOneValue, Model.BoxTwoValue...
private void OnBoxOneChange(PropertyChangedEventArgs e)
{
}
Can't post a full answer without that xaml but if you can pass it a ComboBox via CommandParameter
public RelayCommand<object> BoxChangeCommand { get { return new RelayCommand<object>(OnBoxChange); } }
private void OnBoxChange(Object comboBox)
{
ComboBox list = comboBox as ComboBox;
if (list != null) {
//do stuff
var items = list.Items;
var selectedItem = list.SelectedItem;
}
}
you'll need using System.Windows.Controls for the ComboBox
There is another way too, by binding your SelectedItem in the xaml to your VM and you can press a button on the frontend and the VM with figure everything out.
I have a pretty basic Datagrid XAML bound to a CollectionViewSource.
<DataGrid ItemsSource="{Binding Source={StaticResource EditingItemsCollectionViewSource}}"/>
And the Collection View Source is bound to an observable collection of very basic items with 3 numerical values. C# obviously.
I want to be able to add a new row (add a new item) at the bottom of this datagrid by pressing Tab on the keyboard when I am in the last cell of the last row.
Is this possible?
One possible solution is to programmatically set the property:
dataGrid.AllowUserToAddRows = true;
in order to implement "Add Row" functionality (provided that it was originally set to false, thus the new row was invisible). As per your task definition, it could be triggered by Tab key press (with any additional condition you may add):
private void dataGrid_PreviewKeyDown(object sender, KeyEventArgs e)
{
try
{
if (e.Key == Key.Tab)
{
e.Handled = true;
// your code
}
}
catch{}
}
You may also want to set some default values for newly created row item by adding event handling procedure:
dataGrid.InitializingNewItem += new InitializingNewItemEventHandler(dataGrid_InitNewItem);
private void dataGrid_InitNewItem(object sender, InitializingNewItemEventArgs e)
{
// your code
}
Other sample implementations of adding row to WPF DataGrid could be found here: Wpf DataGrid Add new row
Also, pertinent to your description, you can add the item to the underlying ObservableCollection, so it will automatically appear in the DataGrid.
Hope this will help. Best regards,
Quite a simple question but I think its going to prove much harder than it sounds
I'd like to keep the selection of a listview item there when the focus leaves the list view, at the moment I've set the hideselection property to false and that's fine.. it does cause a VERY light gray selection to stay after the list view loses focus, so my question is, how can I properly show that that item is still selected so that the user will recognize that, something like changing the rows text colour or background colour? or just keeping it highlighted as when first selected the whole row turns blue?
I've had a look through intelisense and can't seem to find anything for a row or item or selected item's individual colour property?
It must exist though because selected items have their own background colour, where would I be able to change that?
Oh and the list view does need to stay in details view, which means I can't use the only method that I've been able to find whilst googling
thanks
Here's a solution for a ListView that does not allow multiple selections and
does not have images (e.g. checkboxes).
Set event handlers for the ListView (in this example it's named listView1):
DrawItem
Leave (invoked when the ListView's focus is lost)
Declare a global int variable (i.e. a member of the Form that contains the ListView,
in this example it's named gListView1LostFocusItem) and assign it the value -1
int gListView1LostFocusItem = -1;
Implement the event handlers as follows:
private void listView1_Leave(object sender, EventArgs e)
{
// Set the global int variable (gListView1LostFocusItem) to
// the index of the selected item that just lost focus
gListView1LostFocusItem = listView1.FocusedItem.Index;
}
private void listView1_DrawItem(object sender, DrawListViewItemEventArgs e)
{
// If this item is the selected item
if (e.Item.Selected)
{
// If the selected item just lost the focus
if (gListView1LostFocusItem == e.Item.Index)
{
// Set the colors to whatever you want (I would suggest
// something less intense than the colors used for the
// selected item when it has focus)
e.Item.ForeColor = Color.Black;
e.Item.BackColor = Color.LightBlue;
// Indicate that this action does not need to be performed
// again (until the next time the selected item loses focus)
gListView1LostFocusItem = -1;
}
else if (listView1.Focused) // If the selected item has focus
{
// Set the colors to the normal colors for a selected item
e.Item.ForeColor = SystemColors.HighlightText;
e.Item.BackColor = SystemColors.Highlight;
}
}
else
{
// Set the normal colors for items that are not selected
e.Item.ForeColor = listView1.ForeColor;
e.Item.BackColor = listView1.BackColor;
}
e.DrawBackground();
e.DrawText();
}
Note: This solution can result in some flicker. A fix for this involves subclassing the ListView control so you
can change the protected property DoubleBuffered to true.
public class ListViewEx : ListView
{
public ListViewEx() : base()
{
this.DoubleBuffered = true;
}
}
I created a class library of the above class so that I could add it to the toolbox.
A possible solution might be this answer to an another question:
How to change listview selected row backcolor even when focus on another control?
I have a program which uses a barcode scanner as input device so that means I need to keep the focus on a text box.
The program has a listview control and I select one of the items programatically when a certain barcode is scanned. I set the background color of the row by:
listviewitem.BackColor = Color.LightSteelBlue;
Things I have tried:
listview.HideSelection set to false
call listview.Focus() after setting the color
listviewitem.Focused set to true
call listview.Invalidate
call listview.Update()
call listview.Refresh()
different combinations of the above
I've also did combinations above stuff in a timer so that they are called on a different thread but still no success.
Any ideas?
More info:
The key here is the control focus. The listview control does not have the focus when I select one of the items.
I select one item by doing:
listView1.Items[index].Selected = true;
the Focus is always in the textbox.
the computer does not have keyboard or mouse, only a barcode reader.
I have this code to keep the focus on the textbox:
private void txtBarcode_Leave(object sender, EventArgs e)
{
this.txtBarcode.Focus();
}
You need to have a textbox add that code to simulate my problem.
What you describe works exactly as expected, assuming that you've set the HideSelection property of the ListView control to False. Here's a screenshot for demonstration purposes. I created a blank project, added a ListView control and a TextBox control to a form, added some sample items to the ListView, set its view to "Details" (although this works in any view), and set HideSelection to false. I handled the TextBox.Leave event just as you showed in the question, and added some simple logic to select the corresponding ListViewItem whenever its name was entered into the TextBox. Notice that "Test Item Six" is selected in the ListView:
Now, as I suspected initially, you're going to mess things up if you go monkeying around with setting the BackColor property yourself. I'm not sure why you would ever want to do this, as the control already uses the default selection colors to indicate selected items by default. If you want to use different colors, you should change your Windows theme, rather than trying to write code to do it.
In fact, if I add the line item.BackColor = Color.LightSteelBlue in addition to my existing code to select the ListViewItem corresponding to the name typed into the TextBox, I get exactly the same thing as shown above. The background color of the item doesn't change until you set focus to the control. That's the expected behavior, as selected items look different when they have the focus than they do when their parent control is unfocused. Selected items on focused controls are painted with the system highlight color; selected items on unfocused controls are painted with the system 3D color. Otherwise, it would be impossible to tell whether or not the ListView control had the focus. Moreover, any custom BackColor property is completely ignored by the operating system when the ListView control has the focus. The background gets painted in the default system highlight color.
Explicitly setting the focus to the ListView control, of course, causes the custom background color to be applied to the ListViewItem, and things render with a color that very much contrasts with the color scheme that I've selected on my computer (remember, not everyone uses the defaults). The problem, though, becomes immediately obvious: you can't set the focus to the ListView control because of the code you've written in the TextBox.Leave event handler method!
I can tell you right now that setting the focus in a focus-changing event is the wrong thing to do. It's a hard rule in Windows you're not allowed to do things like that, and the documentation even warns you explicitly not to do it. Presumably, your answer will be something along the lines of "I have to", but that's no excuse. If everything were working as expected, you wouldn't be asking this question in the first place.
So, what now? Your application's design is broken. I suggest fixing it. Don't try and monkey with setting the BackColor property yourself to indicate that an item is selected. It conflicts with the default way that Windows highlights selected items. Also, don't try and set the focus in a focus-changing event. Windows explicitly forbids this, and the documentation is clear that you're not supposed to do this. If the target computer doesn't have a mouse or keyboard, it's unclear how the user is going to set focus to anything else in the first place, unless you write code to do it, which you shouldn't be doing.
But I have surprisingly little faith that you'll want to fix your application. People who ignore warnings in the documentation tend to be the same people who don't listen to well-meaning advice on Q&A sites. So I'll throw you a bone and tell you how to get the effect you desire anyway. The key lies in not setting the ListViewItem's Selected property, which avoids the conflict between your custom BackColor and the system default highlight color. It also frees you from having to explicitly set the focus to the ListView control and back again (which, as we established above, isn't actually happening, given your Leave event handler method). Doing that produces the following result:
And here's the code—it's not very pretty, but this is just a proof of concept, not a sample of best practice:
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
listView1.View = View.Details;
listView1.HideSelection = false;
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
foreach (ListViewItem item in listView1.Items)
{
if (item.Text == textBox1.Text)
{
item.BackColor = Color.LightSteelBlue;
return;
}
}
}
private void textBox1_Leave(object sender, EventArgs e)
{
this.textBox1.Focus();
}
}
A standard ListView does not let you set the background color of a selected row. The background (and foreground) colors of a selected row are always controlled by the theme of the OS.
You have to owner draw your ListView to get around this OR you can use ObjectListView. ObjectListView is an open source wrapper around .NET WinForms ListView, which makes it much easier to use, as well as easily allowing things that are very difficult in a normal ListView -- like changed the colors of selected rows.
this.objectListView1.UseCustomSelectionColors = true;
this.objectListView1.HighlightBackgroundColor = Color.Lime;
this.objectListView1.UnfocusedHighlightBackgroundColor = Color.Lime;
This shows the ObjectListView when it does not have focus.
Here's a solution for a ListView that does not allow multiple selections and
does not have images (e.g. checkboxes).
Set event handlers for the ListView (in this example it's named listView1):
DrawItem
Leave (invoked when the ListView's focus is lost)
Declare a global int variable (i.e. a member of the Form that contains the ListView,
in this example it's named gListView1LostFocusItem) and assign it the value -1
int gListView1LostFocusItem = -1;
Implement the event handlers as follows:
private void listView1_Leave(object sender, EventArgs e)
{
// Set the global int variable (gListView1LostFocusItem) to
// the index of the selected item that just lost focus
gListView1LostFocusItem = listView1.FocusedItem.Index;
}
private void listView1_DrawItem(object sender, DrawListViewItemEventArgs e)
{
// If this item is the selected item
if (e.Item.Selected)
{
// If the selected item just lost the focus
if (gListView1LostFocusItem == e.Item.Index)
{
// Set the colors to whatever you want (I would suggest
// something less intense than the colors used for the
// selected item when it has focus)
e.Item.ForeColor = Color.Black;
e.Item.BackColor = Color.LightBlue;
// Indicate that this action does not need to be performed
// again (until the next time the selected item loses focus)
gListView1LostFocusItem = -1;
}
else if (listView1.Focused) // If the selected item has focus
{
// Set the colors to the normal colors for a selected item
e.Item.ForeColor = SystemColors.HighlightText;
e.Item.BackColor = SystemColors.Highlight;
}
}
else
{
// Set the normal colors for items that are not selected
e.Item.ForeColor = listView1.ForeColor;
e.Item.BackColor = listView1.BackColor;
}
e.DrawBackground();
e.DrawText();
}
Note: This solution will result in some flicker. A fix for this involves subclassing the ListView control so you
can change the protected property DoubleBuffered to true.
public class ListViewEx : ListView
{
public ListViewEx() : base()
{
this.DoubleBuffered = true;
}
}
On SelectedIndexChanged:
private void lBxDostepneOpcje_SelectedIndexChanged(object sender, EventArgs e)
{
ListViewItem item = lBxDostepneOpcje.FocusedItem as ListViewItem;
ListView.SelectedIndexCollection lista = lBxDostepneOpcje.SelectedIndices;
foreach (Int32 i in lista)
{
lBxDostepneOpcje.Items[i].BackColor = Color.White;
}
if (item != null)
{
item.Selected = false;
if (item.Index == 0)
{
}
else
{
lBxDostepneOpcje.Items[item.Index-1].BackColor = Color.White;
}
if (lBxDostepneOpcje.Items[item.Index].Focused == true)
{
lBxDostepneOpcje.Items[item.Index].BackColor = Color.LightGreen;
if (item.Index < lBxDostepneOpcje.Items.Count-1)
{
lBxDostepneOpcje.Items[item.Index + 1].BackColor = Color.White;
}
}
else if (lBxDostepneOpcje.Items[item.Index].Focused == false)
{
lBxDostepneOpcje.Items[item.Index].BackColor = Color.Blue;
}
}
}
You cant set focus on listview control in this situation. txtBarcode_Leave method will prevent this. But if you are desire to be able select listview items by clicking on them, just add code below to MouseClick event handler of listview:
private void listView1_MouseClick(object sender, MouseEventArgs e)
{
ListView list = sender as ListView;
for (int i = 0; i < list.Items.Count; i++)
{
if (list.Items[i].Bounds.Contains(e.Location) == true)
{
list.Items[i].BackColor = Color.Blue; // highlighted item
}
else
{
list.Items[i].BackColor = SystemColors.Window; // normal item
}
}
}
This change color of selected item. but only in state listview not have focus.
Make sure HideSelection is !TRUE! and simple use this code:
private void ListView_SelectedIndexChanged(object sender, EventArgs e){
foreach(ListViewItem it in ListView.Items)
{
if (it.Selected && it.BackColor != SystemColors.Highlight)
{
it.BackColor = SystemColors.Highlight;
it.ForeColor = SystemColors.HighlightText;
}
if (!it.Selected && it.BackColor != SystemColors.Window)
{
it.BackColor = SystemColors.Window;
it.ForeColor = SystemColors.WindowText;
}
}
}
Just do like this:
Set property UnfocusedHighlighForegroundColor = "Blue"
Set property UnfocusedHighlighBackgroundColor = "White"
Set property UserCustomSelectionColors = true
Good luck :)