What event handler to use for ComboBox Item Selected Selected Item not necessarily changed

Question

Goal  issue an event when items in a combobox drop down list is selected   Problem  Using  SelectionChanged   however  if the user choose the same item as the item is currently being selected then the selection is not changed and therefore this event will not be triggered   Question  What other event handler or other ways  I may use to issue an event regardless of the selected item is changed or not as long as the mouse clicked on that item and that item is being selected    Clarification  Problem is how to trigger  something  when the same item is being selected again  No duplicates in the drop down list  Scenario  first time select item 1 close drop down  And then again  open drop down box and select item 1 when some function are triggered    Solution  for now there seems to be no straight-forward solution to do this  But according to each individual project  there can be ways to work around it   Please update if there are indeed good ways to do this   Thanks

User · Answer

You can use  ComboBoxItem PreviewMouseDown  event  So each time when mouse is down on some item this event will be fired   To add this event in XAML use  ComboBox ItemContainerStyle  like in next example       lt ComboBox x Name  MyBox          ItemsSource   Binding MyList           SelectedValue   Binding MyItem  Mode OneWayToSource    gt           lt ComboBox ItemContainerStyle gt               lt Style gt                   lt EventSetter Event  ComboBoxItem PreviewMouseDown                      Handler  cmbItem PreviewMouseDown   gt               lt  Style gt           lt  ComboBox ItemContainerStyle gt      lt  ComboBox gt    and handle it as usual  void cmbItem PreviewMouseDown object sender  MouseButtonEventArgs e             do your item selection code here        Thanks to MSDN

User · Answer

You can try  SelectedIndexChanged   it will trigger the event even if the same item is selected

User · Answer

I had the same question and I finally found the answer   You need to handle BOTH the SelectionChanged event and the DropDownClosed like this   In XAML    lt ComboBox Name  cmbSelect  SelectionChanged  ComboBox SelectionChanged  DropDownClosed  ComboBox DropDownClosed  gt       lt ComboBoxItem gt 1 lt  ComboBoxItem gt       lt ComboBoxItem gt 2 lt  ComboBoxItem gt       lt ComboBoxItem gt 3 lt  ComboBoxItem gt   lt  ComboBox gt    In C    private bool handle   true  private void ComboBox DropDownClosed object sender  EventArgs e      if handle Handle      handle   true     private void ComboBox SelectionChanged object sender  SelectionChangedEventArgs e      ComboBox cmb   sender as ComboBox    handle    cmb IsDropDownOpen    Handle       private void Handle       switch  cmbSelect SelectedItem ToString   Split new string             StringSplitOptions None  Last               case  1               Handle for the first combobox           break        case  2               Handle for the second combobox           break        case  3               Handle for the third combobox           break

User · Answer

This problem bugs me for a long time since none of the work-around worked for me     But good news is  the following method works fine for my application   The basic idea is to register a EventManager in App xmal cs to sniff PreviewMouseLeftButtonDownEvent for all ComboBoxItem  then trigger the SelectionChangedEvent if the selecting item is the same as the selected item  i e  the selection is performed without changing index   In App xmal cs   public partial class App   Application       protected override void OnStartup StartupEventArgs e                   raise selection change event even when there s no change in index         EventManager RegisterClassHandler typeof ComboBoxItem   UIElement PreviewMouseLeftButtonDownEvent                                            new MouseButtonEventHandler ComboBoxSelfSelection   true            base OnStartup e              private static void ComboBoxSelfSelection object sender  MouseButtonEventArgs e                var item   sender as ComboBoxItem           if  item    null  return              find the combobox where the item resides         var comboBox   ItemsControl ItemsControlFromItemContainer item  as ComboBox           if  comboBox    null  return              fire SelectionChangedEvent if two value are the same         if   string comboBox SelectedValue     string item Content                        comboBox IsDropDownOpen   false              comboBox RaiseEvent new SelectionChangedEventArgs Selector SelectionChangedEvent  new ListItem    new ListItem                          Then  for all combo boxes  register SelectionChangedEvent in a normal way    lt ComboBox ItemsSource   Binding BindList             SelectionChanged  YourSelectionChangedEventHandler   gt    Now  if two indices are different  nothing special but the ordinary event handling process  if two indices are the same  the Mouse Event on the item will first be handled  and thus trigger the SelectionChangedEvent  In this way  both situations will trigger SelectionChangedEvent

User · Answer

private void OnDropDownClosed object sender  EventArgs e          if  combobox SelectedItem    null  return          Do actions

User · Answer

Use SelectionChangeCommitted object sender  EventArgs e  event here

User · Answer

I hope that you will find helpfull the following trick   You can bind both the events  combobox SelectionChanged    OnSelectionChanged  combobox DropDownOpened    OnDropDownOpened    And force selected item to null inside the OnDropDownOpened  private void OnDropDownOpened object sender  EventArgs e        combobox SelectedItem   null      And do what you need with the item inside the OnSelectionChanged  The OnSelectionChanged will be raised every time you will open the combobox  but you can check if SelectedItem is null inside the method and skip the command  private void OnSelectionChanged object sender  SelectionChangedEventArgs e                if  combobox SelectedItem    null                         Do something with the selected item

User · Answer

For UWP  Windows Store  apps none of the above will work  PointerPressed doesn t fire  no Preview  DropDownClosed or SelectedIndexChanged events exist   I had to resort to a transparent button overlaying the ComboBox  but not its drop down arrow   When you press on the arrow  the list drops down as usual and the Combo Box s SelectionChanged event fires  When you click anywhere else on the Combo Box the transparent button s click event fires allowing you to re-select the Combo Box s current value   Some working XAML code                    lt Grid x Name  ComboOverlay  Margin  0 0 5 0  gt   lt  --See comments in code behind at ClickedComboButValueHasntChanged event handler-- gt                       lt ComboBox x Name  NewFunctionSelect  Width  97  ItemsSource   x Bind Functions                             SelectedItem   x Bind ChosenFunction   SelectionChanged  Function SelectionChanged   gt                       lt Button x Name  OldFunctionClick  Height  30  Width  73  Background  Transparent  Click  ClickedComboButValueHasntChanged   gt                   lt  Grid gt    Some working C  code            lt summary gt          It is impossible to simply click a ComboBox to select the shown value again  It always drops down the list of options but             doesn t raise SelectionChanged event if the value selected from the list is the same as before                      To handle this  a transparent button is overlaid over the ComboBox  but not its dropdown arrow  to allow reselecting the old value         Thus clicking over the dropdown arrow allows the user to select a new option from the list  but             clicking anywhere else in the Combo re-selects the previous value          lt  summary gt      private void ClickedComboButValueHasntChanged object sender  RoutedEventArgs e                  You could also dummy up a SelectionChangedEvent event and raise it to invoke Function SelectionChanged handler  below          FunctionEntered NewFunctionSelect SelectedValue as string              private void Function SelectionChanged object sender  SelectionChangedEventArgs e                FunctionEntered e AddedItems 0  as string

User · Answer

This is a DependencyObject for attaching to a ComboBox   It records the currently selected item when the dropdown is opened  and then fires SelectionChanged event if the same index is still selected when the dropdown is closed  It may need to be modified for it to work with Keyboard selection   using System  using System Windows  using System Windows Controls  using System Windows Controls Primitives  using System Web UI WebControls   namespace MyNamespace        public class ComboAlwaysFireSelection   DependencyObject               public static readonly DependencyProperty ActiveProperty   DependencyProperty RegisterAttached               Active               typeof bool               typeof ComboAlwaysFireSelection               new PropertyMetadata false  ActivePropertyChanged             private static void ActivePropertyChanged DependencyObject d  DependencyPropertyChangedEventArgs e                        var element   d as ComboBox              if  element    null                   return               if   e NewValue as bool   GetValueOrDefault false                                 element DropDownClosed    ElementOnDropDownClosed                  element DropDownOpened    ElementOnDropDownOpened                            else                               element DropDownClosed -  ElementOnDropDownClosed                  element DropDownOpened -  ElementOnDropDownOpened                                   private static void ElementOnDropDownOpened object sender  EventArgs eventArgs                         selectedIndex     ComboBox  sender  SelectedIndex                     private static int  selectedIndex           private static void ElementOnDropDownClosed object sender  EventArgs eventArgs                        var comboBox     ComboBox  sender               if  comboBox SelectedIndex     selectedIndex                                comboBox RaiseEvent new SelectionChangedEventArgs Selector SelectionChangedEvent  new ListItemCollection    new ListItemCollection                                        AttachedPropertyBrowsableForChildrenAttribute IncludeDescendants   false            AttachedPropertyBrowsableForType typeof ComboBox            public static bool GetActive DependencyObject  object                        return  bool  object GetValue ActiveProperty                      public static void SetActive DependencyObject  object  bool value                         object SetValue ActiveProperty  value                       and add your namespace prefix to make it accessible    lt UserControl xmlns  http   schemas microsoft com winfx 2006 xaml presentation               xmlns x  http   schemas microsoft com winfx 2006 xaml               xmlns mc  http   schemas openxmlformats org markup-compatibility 2006                xmlns d  http   schemas microsoft com expression blend 2008                xmlns ut  clr-namespace MyNamespace   gt  lt  UserControl gt    and then you need to attach it like so   lt ComboBox ut ComboAlwaysFireSelection Active  True    gt

User · Answer

For UWP  I tried a different approach  I extended the ComboBox class  and processed the SelectionChanged and OnKeyUp events on the ComboBox as well as the Tapped event on the ComboBoxItems  In cases where I get a Tapped event or an Enter or Space key without first getting a SelectionChanged then I know the current item has been re-selected and I respond accordingly   class ExtendedComboBox   ComboBox       public ExtendedComboBox                 SelectionChanged    OnSelectionChanged             protected override void PrepareContainerForItemOverride Windows UI Xaml DependencyObject element  object item                ComboBoxItem cItem   element as ComboBoxItem          if  cItem    null                        cItem Tapped    OnItemTapped                     base PrepareContainerForItemOverride element  item              protected override void OnKeyUp KeyRoutedEventArgs e                   if the user hits the Enter or Space to select an item  then consider this a  reselect  operation         if   e Key    Windows System VirtualKey Space    e Key    Windows System VirtualKey Enter   amp  amp   isSelectionChanged                           handle re-select logic here                    isSelectionChanged   false           base OnKeyUp e                 track whether or not the ComboBox has received a SelectionChanged notification        in cases where it has not yet we get a Tapped or KeyUp notification we will want to consider that a  re-select      bool isSelectionChanged   false      private void OnSelectionChanged object sender  SelectionChangedEventArgs e                isSelectionChanged   true             private void OnItemTapped object sender  TappedRoutedEventArgs e                if   isSelectionChanged                           indicates that an item was re-selected  - handle logic here                    isSelectionChanged   false

User · Answer

Every ComboBoxItem instance has PreviewMouseDown event  If you will subscribe your custom handler on this event on every ComboBoxItem you will have opportunity to handle every click on the dropdown list      Subscribe on ComboBoxItem-s events  comboBox Items Cast lt ComboBoxItem gt    ToList   ForEach i   gt  i PreviewMouseDown    ComboBoxItem PreviewMouseDown    private void ComboBoxItem PreviewMouseDown object sender  MouseButtonEventArgs e            your handler logic

User · Answer

It s easy  just add if  e AddedItems Count    0  return  in the beggining of function like           private  void ComboBox Symbols SelectionChanged object sender  SelectionChangedEventArgs e                if  e AddedItems Count    0           return            Some Other Codes

User · Answer

For me ComboBox DropDownClosed Event did it   private void cbValueType DropDownClosed object sender  EventArgs e                if  cbValueType SelectedIndex    someIntValue    sel ind already updated                          change sel Index of other Combo for example             cbDataType SelectedIndex   someotherIntValue

[c#] What event handler to use for ComboBox Item Selected (Selected Item not necessarily changed)

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