I'm trying to iterate through my Treeview, expanding all nodes however it runs into an InvalidCastException when ran;
Unable to cast object of type 'System.Data.DataRowView' to type 'System.Windows.Controls.TreeViewItem'.
My Code;
foreach (TreeViewItem treeitem in thetreeView.Items)
{
treeitem.IsExpanded = true;
}
Any ideas? I want to fire this from a button.
just add this style
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<Setter Property="IsExpanded" Value="True" />
</Style>
</TreeView.ItemContainerStyle>
for code please go through this link may be this can help u
http://bea.stollnitz.com/blog/?p=55
I've found an "Hackish" solution for that.
It does not involved with inheritance like the solution suggested here (by Kishore Kumar)
I've added two buttons - "Collapse all" and "Expand All".
Code Behind:
private void btnCollapseAll_Click(object sender, RoutedEventArgs e)
{
foreach (var item in treeView.Items)
{
DependencyObject dObject = treeView.ItemContainerGenerator.ContainerFromItem(item);
CollapseTreeviewItems(((TreeViewItem)dObject));
}
}
private void btnExpandAll_Click(object sender, RoutedEventArgs e)
{
foreach (var item in treeView.Items)
{
DependencyObject dObject = treeView.ItemContainerGenerator.ContainerFromItem(item);
((TreeViewItem)dObject).ExpandSubtree();
}
}
private void CollapseTreeviewItems(TreeViewItem Item)
{
Item.IsExpanded = false;
foreach (var item in Item.Items)
{
DependencyObject dObject = treeView.ItemContainerGenerator.ContainerFromItem(item);
if (dObject != null)
{
((TreeViewItem)dObject).IsExpanded = false;
if (((TreeViewItem)dObject).HasItems)
{
CollapseTreeviewItems(((TreeViewItem)dObject));
}
}
}
}
My solution is based on this
Bag of tricks has a demo called "TreeView Expand" that has a tree view with expand all and collapse all buttons (and some more)
Related
Whenever a node is selected in my treeview, it automatically does a horizontal scroll to that item. Is there a way to disable this?
Handle the RequestBringIntoView event and set Handled to true, and the framework won't try to bring the item into view. For example, do something like this in your XAML:
<TreeView>
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<EventSetter Event="RequestBringIntoView" Handler="TreeViewItem_RequestBringIntoView"/>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
And then this in your code-behind:
private void TreeViewItem_RequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
e.Handled = true;
}
I managed to solve the problem using the following:
<TreeView ScrollViewer.HorizontalScrollBarVisibility="Hidden">
<TreeView.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel MaxWidth="{Binding ActualWidth, RelativeSource={RelativeSource AncestorType=ContentPresenter, AncestorLevel=1}}" />
</ItemsPanelTemplate>
</TreeView.ItemsPanel>
</TreeView>
I bind the width of the StackPanel which renders the ItemsPanel here, to the ActualWidth of ContentPresenter in the TreeView.
It also works nice with the "hacked" Stretching TreeView by: http://blogs.msdn.com/b/jpricket/archive/2008/08/05/wpf-a-stretching-treeview.aspx (I modified that solution not to remove grid column, but to change Grid.Column property of the first Decorator element from 1 to 2).
To offer a slightly simplified version of #lena's answer:
To scroll vertically while preserving the horizontal scroll position, and with no unwanted side effects, in the XAML, add event handlers for RequestBringIntoView and Selected:
<TreeView>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<EventSetter Event="RequestBringIntoView" Handler="TreeViewItem_RequestBringIntoView"/>
<EventSetter Event="Selected" Handler="OnSelected"/>
...
In the code behind, add two event handlers:
private void TreeViewItem_RequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
// Ignore re-entrant calls
if (mSuppressRequestBringIntoView)
return;
// Cancel the current scroll attempt
e.Handled = true;
// Call BringIntoView using a rectangle that extends into "negative space" to the left of our
// actual control. This allows the vertical scrolling behaviour to operate without adversely
// affecting the current horizontal scroll position.
mSuppressRequestBringIntoView = true;
TreeViewItem tvi = sender as TreeViewItem;
if (tvi != null)
{
Rect newTargetRect = new Rect(-1000, 0, tvi.ActualWidth + 1000, tvi.ActualHeight);
tvi.BringIntoView(newTargetRect);
}
mSuppressRequestBringIntoView = false;
}
private bool mSuppressRequestBringIntoView;
// Correctly handle programmatically selected items
private void OnSelected(object sender, RoutedEventArgs e)
{
((TreeViewItem)sender).BringIntoView();
e.Handled = true;
}
Matthew, I manged to preserve vertical scrolling, and only prevent horizontal scrolling by restoring the horizontal position after a scroll caused by the RequestBringIntoView event .
private double treeViewHorizScrollPos = 0.0;
private bool treeViewResetHorizScroll = false;
private ScrollViewer treeViewScrollViewer = null;
private void TreeViewItemRequestBringIntoView( object sender, RequestBringIntoViewEventArgs e )
{
if ( this.treeViewScrollViewer == null )
{
this.treeViewScrollViewer = this.DetailsTree.Template.FindName( "_tv_scrollviewer_", this.DetailsTree ) as ScrollViewer;
if( this.treeViewScrollViewer != null )
this.treeViewScrollViewer.ScrollChanged += new ScrollChangedEventHandler( this.TreeViewScrollViewerScrollChanged );
}
this.treeViewResetHorizScroll = true;
this.treeViewHorizScrollPos = this.treeViewScrollViewer.HorizontalOffset;
}
private void TreeViewScrollViewerScrollChanged( object sender, ScrollChangedEventArgs e )
{
if ( this.treeViewResetHorizScroll )
this.treeViewScrollViewer.ScrollToHorizontalOffset( this.treeViewHorizScrollPos );
this.treeViewResetHorizScroll = false;
}
I had a similar problem. I needed to prevent horizontal scroll but preserve vertical scroll. My solution is to handle OnRequestBringIntoView method as I want it to behave. I created a ResourceDictionary for a TreeViewItem and added EventSetters for OnSelected and OnRequestBringIntoView methods.
MyResourceDictionary.xaml
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" x:Class="Resources.MyResourceDictionary" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Style TargetType="TreeViewItem" x:Key="treeitem" >
<EventSetter Event="RequestBringIntoView" Handler="OnRequestBringIntoView"/>
<EventSetter Event="Selected" Handler="OnSelected"/>
</Style>
</ResourceDictionary>
MyResourceDictionary.xaml.cs
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media;
namespace Resources
{
partial class MyResourceDictionary:ResourceDictionary
{
public MyResourceDictionary()
{
InitializeComponent();
}
private void OnRequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
e.Handled = true; //prevent event bubbling
var item = (TreeViewItem)sender;
TreeView tree = GetParentTree(item) as TreeView;
if(tree!=null)
{
var scrollViewer = tree.Template.FindName("_tv_scrollviewer_", tree) as ScrollViewer;
if (scrollViewer != null)
{
scrollViewer.ScrollToLeftEnd();//prevent horizontal scroll
Point relativePoint = item.TransformToAncestor(tree).Transform(new Point(0, 0));//get position of a selected item
if (relativePoint.Y <= scrollViewer.ContentVerticalOffset) return;//do no scroll if we select inside one 'scroll screen'
scrollViewer.ScrollToVerticalOffset(relativePoint.Y);//scroll to Y of a selected item
}
}
}
private DependencyObject GetParentTree(DependencyObject item)
{
var target = VisualTreeHelper.GetParent(item);
return target as TreeView != null ? target : GetParentTree(target);
}
private void OnSelected(object sender, RoutedEventArgs e) //handle programmatically selected items
{
var item = (TreeViewItem)sender;
item.BringIntoView();
e.Handled = true;
}
}
}
Following solution is more simple and fully tested and more compatible, You don't need to calculate and change scrollbar offset, what you need is moving horizontal scrollbar to left, since "RequestBringIntoView" event routing strategy is bubbling, you simply need to do it on last item reached event.
Name scrollViewer control "_tv_scrollviewer_"
<TreeView>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<EventSetter Event="RequestBringIntoView" Handler="TreeViewItem_RequestBringIntoView"/>
On code behind:
private void OnRequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
var item = (TreeViewItem)sender;
if (item != null)
{
// move horizontal scrollbar only when event reached last parent item
if (item.Parent == null)
{
var scrollViewer = itemsTree.Template.FindName("_tv_scrollviewer_", itemsTree) as ScrollViewer;
if (scrollViewer != null)
Dispatcher.BeginInvoke(DispatcherPriority.Loaded, (Action)(() => scrollViewer.ScrollToLeftEnd()));
}
}
}
#lena's solution of preserving vertical scrolling worked best for me. I've iterated on it a little bit:
private void TreeViewItem_RequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
var treeViewItem = (TreeViewItem)sender;
var scrollViewer = treeView.Template.FindName("_tv_scrollviewer_", treeView) as ScrollViewer;
Point topLeftInTreeViewCoordinates = treeViewItem.TransformToAncestor(treeView).Transform(new Point(0, 0));
var treeViewItemTop = topLeftInTreeViewCoordinates.Y;
if (treeViewItemTop < 0
|| treeViewItemTop + treeViewItem.ActualHeight > scrollViewer.ViewportHeight
|| treeViewItem.ActualHeight > scrollViewer.ViewportHeight)
{
// if the item is not visible or too "tall", don't do anything; let them scroll it into view
return;
}
// if the item is already fully within the viewport vertically, disallow horizontal scrolling
e.Handled = true;
}
What this does is let the ScrollViewer scroll normally if the item isn't already in the viewport vertically. However for the actual "annoying" case (where the item is already visible), it sets e.Handled to true, thus preventing horizontal scrolling.
I had a DataGrid that I wanted to do the same operation on and used POHB's answer mostly. I had to modify it for my solution. The code is shown below. The datagrid is a 2 x 2 datagrid with the first column being thin and the second being very wide (1000+). The first column is frozen. I hope this helps someone out. -Matt
public partial class MyUserControl : UserControl
{
private ScrollContentPresenter _scrollContentPresenter;
private ScrollViewer _scrollViewer;
private double _dataGridHorizScrollPos = 0.0;
private bool _dataGridResetHorizScroll = false;
public MyUserControl()
{
// setup code...
_dataGrid.ApplyTemplate();
_scrollViewer = FindVisualChild<ScrollViewer>(_dataGrid);
_scrollViewer.ScrollChanged += new ScrollChangedEventHandler(DataGridScrollViewerScrollChanged);
_scrollContentPresenter = FindVisualChild<ScrollContentPresenter>(_scrollViewer);
_scrollContentPresenter.RequestBringIntoView += new RequestBringIntoViewEventHandler(_scrollContentPresenter_RequestBringInputView);
}
private void DataGridScrollViewerScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (_dataGridResetHorizScroll)
{
_scrollViewer.ScrollToHorizontalOffset(_dataGridHorizScrollPos);
}
// Note: When the row just before a page change is selected and then the next row on the
// next page is selected, a second event fires setting the horizontal offset to 0
// I'm ignoring those large changes by only recording the offset when it's large. -MRB
else if (Math.Abs(e.HorizontalChange) < 100)
{
_dataGridHorizScrollPos = _scrollViewer.HorizontalOffset;
}
_dataGridResetHorizScroll = false;
}
public T FindVisualChild<T>(DependencyObject depObj) where T : DependencyObject
{
if (depObj != null)
{
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
if ((child != null) && (child is ScrollViewer))
{
// I needed this since the template wasn't applied yet when
// calling from the constructor
(child as ScrollViewer).ApplyTemplate();
}
if (child != null && child is T)
{
return (T)child;
}
T childItem = FindVisualChild<T>(child);
if (childItem != null) return childItem;
}
}
return null;
}
private void _scrollContentPresenter_RequestBringInputView(object sender, RequestBringIntoViewEventArgs e)
{
_dataGridResetHorizScroll = true;
}
I want to execute some code when a a selected row of the WPF DataGrid is double clicked. I know that the datagrid has a MouseDoubleClicked event and that it also has a row selected event but I don't see any event for "selected row double clicked" ...
Do you think it's possible to capture this event somehow ?
you can add the event handler in the ItemContainerStyle (which is the style applied to a row) :
<DataGrid ... >
<DataGrid.ItemContainerStyle>
<Style TargetType="DataGridRow">
<EventSetter Event="MouseDoubleClick" Handler="Row_DoubleClick"/>
</Style>
</DataGrid.ItemContainerStyle>
...
</DataGrid>
Then, in the handler, you can check if the row is selected
private void Row_DoubleClick(object sender, MouseButtonEventArgs e)
{
// execute some code
}
This question came up for me while looking for a solution and the answers didn't work, whether due to age or my own implementation. Either way, here is the solution that worked for me.
Add the MouseDoubleClick event to the DataGrid
<DataGrid x:Name="DatagridMovie"
Width="Auto"
CanUserAddRows="False"
CanUserDeleteRows="True"
IsReadOnly="true"
ItemsSource="{Binding}"
MouseDoubleClick="Row_MouseDoubleClick">
and in the method
private void Row_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
// Ensure row was clicked and not empty space
var row = ItemsControl.ContainerFromElement((DataGrid)sender,
e.OriginalSource as DependencyObject) as DataGridRow;
if ( row == null ) return;
… Stuff();
}
So far I haven't noticed any problems with it. It doesn't share the problem that others have that means double clicking a header or empty space with a row selected beforehand would still cause it to run.
With data binding and MVVM you would do one-click event (=selectedItem of row) like this:
<Datagrid ItemsSource="{Binding YourObservableCollectionProperty}"
SelectedItem="{Binding YourSelectedItemProperty}">
//more...
</Datagrid>
CodeBehind:
public partial class YourClass : Window
{
public YourClass()
{
InitializeComponent();
this.DataContext = new YourClassViewModel();
}
}
ViewModel:
public class YourClassViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
public virtual void OnPropertyChanged(string propertyName)
{
if (this.PropertyChanged != null)
{
this.PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
private ObservableCollection<YourModelClass> _yourObservableCollectionProperty;
public ObservableCollection<YourModelClass> YourObservableCollectionProperty
{
get { return _yourObservableCollectionProperty; }
set
{
_yourObservableCollectionProperty = value;
OnPropertyChanged("YourObservableCollectionProperty");
}
}
private YourModelClass _yourSelectedItemProperty;
public YourModelClass YourSelectedItemProperty
{
get { return _yourSelectedItemProperty; }
set
{
_yourSelectedItemProperty = value;
OnPropertyChanged("YourSelectedItemProperty");
}
}
//Constructor
public YourClassViewModel()
{
/*Take your ModelClass instance and ObservableCollection instance here
and play around with them or move them into a method. Normally your
observablecollection is the itemssource of your datagrid and your selecteditem
is your modelclass.*/
}
}
You could try current cell changed event handler it works only with one click and not double click if thats what your looking for, since double click can be used to for initiating editing cell or entire row or for any other process:
private void datagrid_CurrentCellChanged(object sender, EventArgs e)
{
int selected_index = datagrid.SelectedIndex + 1;
// this is used for debugging and testing.
//MessageBox.Show("The index of the row for the clicked cell is " + selected_index);
}
The ItemContainerStyle do not have best solution, suggest use the RowStyle:
In your XAML:
<DataGrid.RowStyle>
<Style TargetType="DataGridRow">
<EventSetter Event="MouseDoubleClick" Handler="DataGridRow_MouseDoubleClick"/>
</Style>
</DataGrid.RowStyle>
In your Code:
private void DataGridRow_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
//your logic here
}
Why don't you get the SelectedRow property while the DoubleClick event happens and do something with it? If the SelectedRow is null, it means no Row is selected so just return
private void Grid_DoubleClick(object sender, RoutedEventArgs e)
{
if(grid.SelectedRow == null)
return; // return if there's no row selected
// do something with the Selected row here
}
Use rowstyle and MouseDoubleClick work, like Darlan Dieterich said.
But when there are button or checkbox or other controls in cell, they will handle event but not prevent event passing to row, cause weird behavior. Use MouseDown maybe better in these case.
<DataGrid.RowStyle>
<Style TargetType="DataGridRow">
<EventSetter Event="MouseDown" Handler="DataGridRow_MouseDown"/>
</Style>
</DataGrid.RowStyle>
private void DataGridRow_MouseDown(object sender, MouseButtonEventArgs e)
{
if(e.ClickCount != 2)
{
return;
}
// code here
e.Handled = true;
}
When I expand items in my treeview so that scrolling is necessary, a scrollbar appears. However, it doesn't scroll down for the newly expanded branch of items - they get cropped by the bottom of the control. So as I continue expanding items at the bottom of the tree, I have to keep manually scrolling down to see the new children. Anyone have a suggestion for how make it automatically scroll to show the newly expanded items?
You can use a simple EventSetter in TreeViewItem style to invoke an event handler when the item is selected. Then call BringIntoView for the item.
<TreeView >
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<EventSetter Event="Selected" Handler="TreeViewSelectedItemChanged" />
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
private void TreeViewSelectedItemChanged(object sender, RoutedEventArgs e)
{
TreeViewItem item = sender as TreeViewItem;
if (item != null)
{
item.BringIntoView();
e.Handled = true;
}
}
On the TreeView, handle the TreeViewItem.Expanded event (you can do this at the TreeView level because of event bubbling). In the Expanded handler, call BringIntoView on the TreeViewItem that raised the event.
You may need a bit of trial and error to get hold of the TreeViewItem in your event handler code. I think (haven't checked) that the sender argument to your Expanded event handler will be the TreeView (since that's where the event handler is attached) rather than the TreeViewItem. And the e.Source or e.OriginalSource may be an element in the TreeViewItem's data template. So you may need to use VisualTreeHelper to walk up the visual tree to find the TreeViewItem. But if you use the debugger to inspect the sender and the RoutedEventArgs this should be trivial to figure out.
(If you're able to get this working and want to bundle it up so you don't have to attach the same event handler to every TreeView, it should be easy to encapsulate it as an attached behaviour which will allow you to apply it declaratively, including via a Style.)
Use a dependency property on an IsSelected trigger:
<Style TargetType="{x:Type TreeViewItem}">
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="commands:TreeViewItemBehavior.BringIntoViewWhenSelected" Value="True" />
</Trigger>
</Style.Triggers>
Here's the code for the dependency property:
public static bool GetBringIntoViewWhenSelected(TreeViewItem treeViewItem)
{
return (bool)treeViewItem.GetValue(BringIntoViewWhenSelectedProperty);
}
public static void SetBringIntoViewWhenSelected(TreeViewItem treeViewItem, bool value)
{
treeViewItem.SetValue(BringIntoViewWhenSelectedProperty, value);
}
public static readonly DependencyProperty BringIntoViewWhenSelectedProperty =
DependencyProperty.RegisterAttached("BringIntoViewWhenSelected", typeof(bool),
typeof(TreeViewItemBehavior), new UIPropertyMetadata(false, OnBringIntoViewWhenSelectedChanged));
static void OnBringIntoViewWhenSelectedChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e)
{
TreeViewItem item = depObj as TreeViewItem;
if (item == null)
return;
if (e.NewValue is bool == false)
return;
if ((bool)e.NewValue)
item.BringIntoView();
}
Thanks to itowlson's answer, here's the expanded event handler code that works for both of my trees
private static void Tree_Expanded(object sender, RoutedEventArgs e)
{
// ignore checking, assume original source is treeviewitem
var treeViewItem = (TreeViewItem)e.OriginalSource;
var count = VisualTreeHelper.GetChildrenCount(treeViewItem);
for (int i = count - 1; i >= 0; --i)
{
var childItem = VisualTreeHelper.GetChild(treeViewItem, i);
((FrameworkElement)childItem).BringIntoView();
}
// do NOT call BringIntoView on the actual treeviewitem - this negates everything
//treeViewItem.BringIntoView();
}
I modified Jared's answer in combination with the strategy from here: https://stackoverflow.com/a/42238409/2477582
The main advantage is that there aren't n calls of BringIntoView() for n childs. There is only one call of BringIntoView for an area that covers all of the child's heights.
Additionally, the purpose of the referred topic is realized as well. But this part may be removed, if unwanted.
/// <summary>Prevents automatic horizontal scrolling, while preserving automatic vertical scrolling and other side effects</summary>
/// <remarks>Source: https://stackoverflow.com/a/42238409/2477582 </remarks>
private void TreeViewItem_RequestBringIntoView(object sender, RequestBringIntoViewEventArgs e)
{
// Ignore re-entrant calls
if (m_SuppressRequestBringIntoView)
return;
// Cancel the current scroll attempt
e.Handled = true;
// Call BringIntoView using a rectangle that extends into "negative space" to the left of our
// actual control. This allows the vertical scrolling behaviour to operate without adversely
// affecting the current horizontal scroll position.
m_SuppressRequestBringIntoView = true;
try
{
TreeViewItem tvi = sender as TreeViewItem;
if (tvi != null)
{
// take care of children
int ll_ChildCount = VisualTreeHelper.GetChildrenCount(tvi);
double ll_Height = tvi.ActualHeight;
if (ll_ChildCount > 0)
{
FrameworkElement ll_LastChild = VisualTreeHelper.GetChild(tvi, ll_ChildCount - 1) as FrameworkElement;
ll_Height += ll_ChildCount * ll_LastChild.ActualHeight;
}
Rect newTargetRect = new Rect(-1000, 0, tvi.ActualWidth + 1000, ll_Height);
tvi.BringIntoView(newTargetRect);
}
}
catch (Exception ex)
{
m_Log.Debug("Error in TreeViewItem_RequestBringIntoView: " + ex.ToString());
}
m_SuppressRequestBringIntoView = false;
}
The above solution works together with this:
/// <summary>Correctly handle programmatically selected items (needed due to the custom implementation of TreeViewItem_RequestBringIntoView)</summary>
/// <remarks>Source: https://stackoverflow.com/a/42238409/2477582 </remarks>
private void TreeViewItem_Selected(object sender, RoutedEventArgs e)
{
((TreeViewItem)sender).BringIntoView();
e.Handled = true;
}
This part takes care of toggling the elements at each click:
/// <summary>Support for single click toggle</summary>
private void TreeViewItem_MouseUp(object sender, MouseButtonEventArgs e)
{
TreeViewItem tvi = null;
// Source may be TreeViewItem directly, or be a ContentPresenter
if (e.Source is TreeViewItem)
{
tvi = e.Source as TreeViewItem;
}
else if (e.Source is ContentPresenter)
{
tvi = (e.Source as ContentPresenter).TemplatedParent as TreeViewItem;
}
if (tvi == null || e.Handled) return;
tvi.IsExpanded = !tvi.IsExpanded;
e.Handled = true;
}
Finally the XAML part:
<TreeView>
<TreeView.ItemContainerStyle>
<Style TargetType="TreeViewItem">
<EventSetter Event="RequestBringIntoView" Handler="TreeViewItem_RequestBringIntoView" />
<EventSetter Event="Selected" Handler="TreeViewItem_Selected" />
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
A simple event listener on the tree worked for me:
<TreeView Margin="10,40,10,10" Grid.Column="0" x:Name="treeView" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" SelectedItemChanged="TreeView_SelectedItemChanged" />
private void TreeView_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e) {
if (e.NewValue == null)
return;
((TreeViewItem)e.NewValue).BringIntoView();
}
I've almost got this working apart from one little annoying thing...
Because the ListBox selection happens on mouse down, if you start the drag with the mouse down when selecting the last item to drag it works fine, but if you select all the items to drag first and then click on the selection to start dragging it, the one you click on gets unselected and left behind after the drag.
Any thoughts on the best way to get around this?
<DockPanel LastChildFill="True">
<ListBox ItemsSource="{Binding SourceItems}"
SelectionMode="Multiple"
PreviewMouseLeftButtonDown="HandleLeftButtonDown"
PreviewMouseLeftButtonUp="HandleLeftButtonUp"
PreviewMouseMove="HandleMouseMove"
MultiSelectListboxDragDrop:ListBoxExtension.SelectedItemsSource="{Binding SelectedItems}"/>
<ListBox ItemsSource="{Binding DestinationItems}"
AllowDrop="True"
Drop="DropOnToDestination"/>
<DockPanel>
...
public partial class Window1
{
private bool clickedOnSourceItem;
public Window1()
{
InitializeComponent();
DataContext = new WindowViewModel();
}
private void DropOnToDestination(object sender, DragEventArgs e)
{
var viewModel = (WindowViewModel)
e.Data.GetData(typeof(WindowViewModel));
viewModel.CopySelectedItems();
}
private void HandleLeftButtonDown(object sender, MouseButtonEventArgs e)
{
var sourceElement = (FrameworkElement)sender;
var hitItem = sourceElement.InputHitTest(e.GetPosition(sourceElement))
as FrameworkElement;
if(hitItem != null)
{
clickedOnSourceItem = true;
}
}
private void HandleLeftButtonUp(object sender, MouseButtonEventArgs e)
{
clickedOnSourceItem = false;
}
private void HandleMouseMove(object sender, MouseEventArgs e)
{
if(clickedOnSourceItem)
{
var sourceItems = (FrameworkElement)sender;
var viewModel = (WindowViewModel)DataContext;
DragDrop.DoDragDrop(sourceItems, viewModel, DragDropEffects.Move);
clickedOnSourceItem = false;
}
}
}
I've found a very simple way to enable Windows Explorer like drag/drop behaviour when having multiple items selected. The solution replaces the common ListBox with a little derived shim that replaces the ListBoxItem with a more intelligent version. This way, we can encapsulate the click state at the right level and call into the protected selection machinery of the ListBox. Here is the relevant class. For a complete example, see my repo on github.
public class ListBoxEx : ListBox
{
protected override DependencyObject GetContainerForItemOverride()
{
return new ListBoxItemEx();
}
class ListBoxItemEx : ListBoxItem
{
private bool _deferSelection = false;
protected override void OnMouseLeftButtonDown(MouseButtonEventArgs e)
{
if (e.ClickCount == 1 && IsSelected)
{
// the user may start a drag by clicking into selected items
// delay destroying the selection to the Up event
_deferSelection = true;
}
else
{
base.OnMouseLeftButtonDown(e);
}
}
protected override void OnMouseLeftButtonUp(MouseButtonEventArgs e)
{
if (_deferSelection)
{
try
{
base.OnMouseLeftButtonDown(e);
}
finally
{
_deferSelection = false;
}
}
base.OnMouseLeftButtonUp(e);
}
protected override void OnMouseLeave(MouseEventArgs e)
{
// abort deferred Down
_deferSelection = false;
base.OnMouseLeave(e);
}
}
}
So...having become the proud owner of a tumbleweed badge, I've got back on to this to try & find a way around it. ;-)
I'm not sure I like the solution so I'm still very much open to any better approaches.
Basically, what I ended up doing is remember what ListBoxItem was last clicked on & then make sure that gets added to the selected items before a drag. This also meant looking at how far the mouse moves before starting a drag - because clicking on a selected item to unselect it could sometimes result in it getting selected again if mouse bounce started a little drag operation.
Finally, I added some hot tracking to the listbox items so, if you mouse down on a selected item it'll get unselected but you still get some feedback to indicate that it will get included in the drag operation.
private void HandleLeftButtonDown(object sender, MouseButtonEventArgs e)
{
var source = (FrameworkElement)sender;
var hitItem = source.InputHitTest(e.GetPosition(source)) as FrameworkElement;
hitListBoxItem = hitItem.FindVisualParent<ListBoxItem>();
origPos = e.GetPosition(null);
}
private void HandleLeftButtonUp(object sender, MouseButtonEventArgs e)
{
hitListBoxItem = null;
}
private void HandleMouseMove(object sender, MouseEventArgs e)
{
if (ShouldStartDrag(e))
{
hitListBoxItem.IsSelected = true;
var sourceItems = (FrameworkElement)sender;
var viewModel = (WindowViewModel)DataContext;
DragDrop.DoDragDrop(sourceItems, viewModel, DragDropEffects.Move);
hitListBoxItem = null;
}
}
private bool ShouldStartDrag(MouseEventArgs e)
{
if (hitListBoxItem == null)
return false;
var curPos = e.GetPosition(null);
return
Math.Abs(curPos.Y-origPos.Y) > SystemParameters.MinimumVerticalDragDistance ||
Math.Abs(curPos.X-origPos.X) > SystemParameters.MinimumHorizontalDragDistance;
}
XAML changes to include hot tracking...
<Style TargetType="ListBoxItem">
<Setter Property="Margin" Value="1"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListBoxItem}">
<Grid>
<Border Background="{TemplateBinding Background}" />
<Border Background="#BEFFFFFF" Margin="1">
<Grid>
<Grid.RowDefinitions>
<RowDefinition /><RowDefinition />
</Grid.RowDefinitions>
<Border Margin="1" Grid.Row="0" Background="#57FFFFFF" />
</Grid>
</Border>
<ContentPresenter Margin="8,5" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="Background" Value="PowderBlue" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsMouseOver" Value="True" />
<Condition Property="IsSelected" Value="False"/>
</MultiTrigger.Conditions>
<Setter Property="Background" Value="#5FB0E0E6" />
</MultiTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
One option would be not to allow ListBox or ListView to remove selected items until MouseLeftButtonUp is triggered.
Sample code:
List<object> removedItems = new List<object>();
private void ListBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (e.RemovedItems.Count > 0)
{
ListBox box = sender as ListBox;
if (removedItems.Contains(e.RemovedItems[0]) == false)
{
foreach (object item in e.RemovedItems)
{
box.SelectedItems.Add(item);
removedItems.Add(item);
}
}
}
}
private void ListBox_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
if (removedItems.Count > 0)
{
ListBox box = sender as ListBox;
foreach (object item in removedItems)
{
box.SelectedItems.Remove(item);
}
removedItems.Clear();
}
}
I'm surprised that the behaviour difference between ListBox and the Windows Explorer has not been taken care of after 4 years across 3 major updates of the .NET framework.
I ran in to this problem back in Silverlight 3. I ended up overriding the mouse down and mouse up event handler to fully simulate the Windows Explorer behaviour.
I don't have the source code any more but the logic should be:
When mouse down
if the target item is not selected, clear existing selection
if Ctrl key is down, add target item to selection
if Shift key is down
if there is a previously selected item, add all items between target item and previous item to selection
else only add target item to selection
if the target item is selected de-select only if Ctrl key is down
When mouse up (on the same item)
if the target item is selected
if Ctrl key is down, remove item from selection
if Shift key is down
if there is a previously selected item, remove all items between target item and previous item from selection
else only remove target item from selection
However
This should really be Microsoft's job to update the behaviour to be consistent to the operating system and to be more intuitive. I've submitted it as a bug to Microsoft if any body wants to vote for it: http://connect.microsoft.com/VisualStudio/feedback/details/809192/
I had a similar problem. I Started with the basic implementation from https://www.c-sharpcorner.com/uploadfile/dpatra/drag-and-drop-item-in-listbox-in-wpf/
and Modified to something like this:
ListBox dragSource = null;
ObservableCollection<String> dragItems;
private void ListBox_Drop(object sender, DragEventArgs e)
{
ListBox parent = (ListBox)sender;
// check if the Items are from an different source
if(dragSource != parent)
{
// Add and remove the Items of both sources
foreach (var item in dragItems)
{
((ObservableCollection<String>)dragSource.ItemsSource).Remove(item);
((ObservableCollection<String>)parent.ItemsSource).Add(item);
}
}
}
private void ListBox_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
// Check if Modifiers for Selection modes are pressed
if(Keyboard.Modifiers != ModifierKeys.Control && Keyboard.Modifiers != ModifierKeys.Shift)
{
ListBox parent = (ListBox)sender;
dragSource = parent;
object data = GetDataFromListBox(dragSource, e.GetPosition(parent));
dragItems = new ObservableCollection<String>();
for(int i = 0; i < parent.SelectedItems.Count; i++)
{
dragItems.Add(parent.SelectedItems[i] as String);
}
//If the Data is currently selected drop whole selection
if(dragItems.Contains(data as String))
{
DragDrop.DoDragDrop(parent, parent.SelectedItems, DragDropEffects.Move);
}
// The data is not selected, so clear selection and try to drop the current Item
else
{
dragItems.Clear();
dragItems.Add(data as String);
parent.SelectedItems.Clear();
DragDrop.DoDragDrop(parent, data, DragDropEffects.Move);
}
}
}
private static object GetDataFromListBox(ListBox source, Point point)
{
UIElement element = source.InputHitTest(point) as UIElement;
if (element != null)
{
object data = DependencyProperty.UnsetValue;
while (data == DependencyProperty.UnsetValue)
{
data = source.ItemContainerGenerator.ItemFromContainer(element);
if (data == DependencyProperty.UnsetValue)
{
element = VisualTreeHelper.GetParent(element) as UIElement;
}
if (element == source)
{
return null;
}
}
if (data != DependencyProperty.UnsetValue)
{
return data;
}
}
return null;
}
Hope this helps anyone to sumples across this Thread
How can the handler method of a WPF menu item determine which item in a ListView was clicked on?
Edit:
The menu is a context menu which has been set for the ListView. The problem is to find which ListView item has been clicked on when the context menu item is selected.
Checkout ContextMenu.PlacementTarget, which that object you can walk up the visual tree (VisualTreeHelper.GetParent) until you find a ListViewItem.
Just in case anyone else has this problem, I ended up with something like:
private void ListViewItems_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
var frameworkElement = e.OriginalSource as FrameworkElement;
var item = frameworkElement.DataContext as MyDataItem;
if(null == item)
{
return;
}
// TODO: Use item here...
}
If each of your data items has an IsSelected property that is bound to the ListViewItem.IsSelected property, then you just iterate through your data to find the selected ones:
<ListView ItemsSource="{Binding Items}">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="IsSelected" Value="{Binding IsSelected}"/>
</Style>
</ListView.ItemContainerStyle>
</ListView>
And in your code:
public ICollection<DataItem> Items
{
get { return _items; }
}
public IEnumerable<DataItem> SelectedItems
{
get
{
foreach (var item in Items)
{
if (item.IsSelected)
yield return item;
}
}
}
private void DoSomethingWithSelectedItems()
{
foreach (var item in SelectedItems) ...
}