I'm using below code for fix my screen when i insert listboxItem.
public partial class KeepItemsInViewListBox : ListBox
{
private ScrollViewer ScrollViewer { get; set; }
#region Overrides of FrameworkElement
/// <inheritdoc />
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
if (TryFindVisualChildElement(this, out ScrollViewer scrollViewer))
{
this.ScrollViewer = scrollViewer;
}
}
#endregion
#region Overrides of ListView
/// <inheritdoc />
protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
{
base.OnItemsChanged(e);
if (this.ScrollViewer == null)
{
return;
}
double verticalOffset;
switch (e.Action)
{
case NotifyCollectionChangedAction.Add when e.NewItems != null:
// Check if insert or add
verticalOffset = e.NewStartingIndex < this.ScrollViewer.VerticalOffset
? this.ScrollViewer.VerticalOffset + e.NewItems.Count
: this.ScrollViewer.VerticalOffset;
break;
case NotifyCollectionChangedAction.Remove when e.OldItems != null:
verticalOffset = this.ScrollViewer.VerticalOffset - e.OldItems.Count;
break;
default:
verticalOffset = this.ScrollViewer.VerticalOffset;
break;
}
this.ScrollViewer?.ScrollToVerticalOffset(verticalOffset);
}
#endregion
public bool TryFindVisualChildElement<TChild>(DependencyObject parent, out TChild childElement)
where TChild : FrameworkElement
{
childElement = null;
if (parent == null)
{
return false;
}
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, i);
if (child is TChild resultElement)
{
childElement = resultElement;
return true;
}
if (TryFindVisualChildElement(child, out childElement))
{
return true;
}
}
return false;
}
}
that class makes my listbox's scroll to item-by-item.
see the below picture.
before upper Class(KeepItemsInViewListBox), my scrolling condition is Pixel. but after using that code my scrolling condition is changed.
because all of my listboxitem's size is diffrent,
I added VirtualizingPanel.ScrollUnit="Pixel" or ScrollViewer.CanContentScroll = "False" in xaml, or ScrollViewer.CanContentScroll = false; in .cs file
then my screen is also move...
First thanks to Mr.Code
I modify Mr.Code's class, but my Code is not a perfect.
public class KeepItemsInViewListBox : ListBox
{
private ScrollViewer ScrollViewer { get; set; }
private void ScrollViewer_ScrollChanged(object sender, ScrollChangedEventArgs e)
{
if (insertCheck)
{
ScrollViewer.ScrollToVerticalOffset(ScrollViewer.VerticalOffset + e.ExtentHeightChange);
insertCheck = false;
}
}
#region Overrides of FrameworkElement
/// <inheritdoc />
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
if (TryFindVisualChildElement(this, out ScrollViewer scrollViewer))
{
this.ScrollViewer = scrollViewer;
ScrollViewer.ScrollChanged += ScrollViewer_ScrollChanged;
}
}
#endregion
private bool insertCheck = false;
#region Overrides of ListView
/// <inheritdoc />
protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
{
base.OnItemsChanged(e);
switch (e.Action)
{
case NotifyCollectionChangedAction.Add when e.NewItems != null:
bool isInsert = this.ScrollViewer.CanContentScroll
? e.NewStartingIndex < this.ScrollViewer.VerticalOffset
: e.NewStartingIndex + 1 != this.Items.Count - 1;
if (!isInsert)
{
return;
}
insertCheck = isInsert;
break;
}
}
#endregion
public bool TryFindVisualChildElement<TChild>(DependencyObject parent, out TChild childElement)
where TChild : FrameworkElement
{
childElement = null;
if (parent == null)
{
return false;
}
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(parent); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(parent, i);
if (child is TChild resultElement)
{
childElement = resultElement;
return true;
}
if (TryFindVisualChildElement(child, out childElement))
{
return true;
}
}
return false;
}
}
I just redefine "ScrollViewer_ScrollChanged" method and set verticalOffset to changed offset value.
It works in my test Project. but in my real Project doesn't work. Then i use ScrollViewer's ExtentHeight value.
I checked the first ExtentHeight and it was saved. After scrolling, I compare two of ExtentHeight and set the diffrence to verticalOffset.
But it isn't work Beautifully
I need to get the position of a WPF DataGridCell, obtained in a DataGrid cell changed event, but only can get the vertical (Y-axis).
The horizontal remains the same, despite a different column is pointed.
Here is the almost working code.
Test by clicking on different cells.
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
List<Person> Persons = new List<Person>();
public MainWindow()
{
InitializeComponent();
Persons.Add(new Person { Id = 1, Name = "John", City = "London" });
Persons.Add(new Person { Id = 2, Name = "Charles", City = "Rome" });
Persons.Add(new Person { Id = 3, Name = "Paul", City = "Chicago" });
this.EditingDataGrid.ItemsSource = Persons;
this.EditingDataGrid.CurrentCellChanged += new EventHandler<EventArgs>(EditingDataGrid_CurrentCellChanged);
}
void EditingDataGrid_CurrentCellChanged(object sender, EventArgs e)
{
DataGridCell Cell = GetCurrentCell(this.EditingDataGrid);
var Position = Cell.PointToScreen(new Point(0, 0));
// WHY X NEVER CHANGES??!!
MessageBox.Show("X=" + Position.X.ToString() + ", Y=" + Position.Y.ToString(), "Position");
}
/// <summary>
/// Returns, for this supplied Source Data-Grid, the current Data-Grid-Cell.
/// May return null if no associated Cell is found.
/// </summary>
public static DataGridCell GetCurrentCell(DataGrid SourceDataGrid)
{
if (SourceDataGrid.CurrentCell == null)
return null;
var RowContainer = SourceDataGrid.ItemContainerGenerator.ContainerFromItem(SourceDataGrid.CurrentCell.Item);
if (RowContainer == null)
return null;
var RowPresenter = GetVisualChild<System.Windows.Controls.Primitives.DataGridCellsPresenter>(RowContainer);
if (RowPresenter == null)
return null;
var Container = RowPresenter.ItemContainerGenerator.ContainerFromItem(SourceDataGrid.CurrentCell.Item);
var Cell = Container as DataGridCell;
// Try to get the cell if null, because maybe the cell is virtualized
if (Cell == null)
{
SourceDataGrid.ScrollIntoView(RowContainer, SourceDataGrid.CurrentCell.Column);
Container = RowPresenter.ItemContainerGenerator.ContainerFromItem(SourceDataGrid.CurrentCell.Item);
Cell = Container as DataGridCell;
}
return Cell;
}
/// <summary>
/// Returns the nearest child having the specified TRet type for the supplied Target.
/// </summary>
public static TRet GetVisualChild<TRet>(DependencyObject Target) where TRet : DependencyObject
{
if (Target == null)
return null;
for (int ChildIndex = 0; ChildIndex < VisualTreeHelper.GetChildrenCount(Target); ChildIndex++)
{
var Child = VisualTreeHelper.GetChild(Target, ChildIndex);
if (Child != null && Child is TRet)
return (TRet)Child;
else
{
TRet childOfChild = GetVisualChild<TRet>(Child);
if (childOfChild != null)
return childOfChild;
}
}
return null;
}
}
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
public string City { get; set; }
}
The DataGrid is just defined by...
<DataGrid x:Name="EditingDataGrid"/>
Maybe exists there an alternative to get that DataGridCell position?
You can get the DataGridCell from CurrentCell like this
void EditingDataGrid_CurrentCellChanged(object sender, EventArgs e)
{
DataGridCell Cell = GetDataGridCell(EditingDataGrid.CurrentCell);
var Position = Cell.PointToScreen(new Point(0, 0));
MessageBox.Show("X=" + Position.X.ToString() + ", Y=" + Position.Y.ToString(), "Position");
}
public static DataGridCell GetDataGridCell(DataGridCellInfo cellInfo)
{
if (cellInfo.IsValid == false)
{
return null;
}
var cellContent = cellInfo.Column.GetCellContent(cellInfo.Item);
if (cellContent == null)
{
return null;
}
return cellContent.Parent as DataGridCell;
}
You could also create an extension method on the DataGrid to do this
DataGridExtensions.cs
public static class DataGridExtensions
{
public static DataGridCell GetCurrentDataGridCell(this DataGrid dataGrid)
{
DataGridCellInfo cellInfo = dataGrid.CurrentCell;
if (cellInfo.IsValid == false)
{
return null;
}
var cellContent = cellInfo.Column.GetCellContent(cellInfo.Item);
if (cellContent == null)
{
return null;
}
return cellContent.Parent as DataGridCell;
}
}
Which you can use like this everytime you want to get the current DataGridCell
DataGridCell Cell = EditingDataGrid.GetCurrentDataGridCell();
I guess what's going on is that your grid's default selection mode is full row, the code you're using to get the DataGridCell is getting the first selected cell which holds the "Id" column value.
What you can try to do is changing the grid's selection mode to "Cell" and this trigger the message box with correct coordinates.
<DataGrid x:Name="EditingDataGrid" SelectionUnit="Cell"/>
Also I've changed your code a bit, see if it would work for you:
void EditingDataGrid_CurrentCellChanged(object sender, EventArgs e)
{
// this will iterate through all selected cell of the datagrid
foreach (DataGridCellInfo cellInfo in this.EditingDataGrid.SelectedCells)
{
DataGridCell Cell = GetCurrentCell(this.EditingDataGrid, cellInfo);
if (Cell != null)
{
var Position = Cell.PointToScreen(new Point(0, 0));
MessageBox.Show("X=" + Position.X.ToString() +
", Y=" + Position.Y.ToString() +
" Content = " + ((TextBlock)Cell.Content).Text.ToString(), "Position");
}
}
}
/// <summary>
/// Returns, for this supplied Source Data-Grid, the current Data-Grid-Cell.
/// May return null if no associated Cell is found.
/// </summary>
public static DataGridCell GetCurrentCell(DataGrid grid, DataGridCellInfo cellInfo)
{
DataGridCell result = null;
DataGridRow row = (DataGridRow)grid.ItemContainerGenerator.ContainerFromItem(cellInfo.Item);
if (row != null)
{
int columnIndex = grid.Columns.IndexOf(cellInfo.Column);
if (columnIndex > -1)
{
DataGridCellsPresenter presenter = GetVisualChild<DataGridCellsPresenter>(row);
result = presenter.ItemContainerGenerator.ContainerFromIndex(columnIndex) as DataGridCell;
}
}
return result;
}
/// <summary>
/// Returns the nearest child having the specified TRet type for the supplied Target.
/// </summary>
static T GetVisualChild<T>(Visual parent) where T : Visual
{
T child = default(T);
int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < numVisuals; i++)
{
Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
child = v as T;
if (child == null)
{
child = GetVisualChild<T>(v);
}
if (child != null)
{
break;
}
}
return child;
}
hope this helps, regards
I currently have a ListBox whose ItemsSource collection is bound to a property on my viewmodel, of type IEnumerable. When that preoprty's reference changes, the ListBox updates as expected, however I have a problem in that if I have a large collection of items and scroll to the bottom of the ListBox, and then change the reference to another collection containing, say, 1 item, the ListBox view is blank and no scrollbar is displayed. I have to then scroll the listbox up with the mouse wheel, until the 1 item comes into view.
So, what I think I'm after, is a way of resetting the scroll position of the ListBox to the top, whenever the ItemsSource property changes, so that something is always displayed no matter how large or small the collection.
I'm unable to reproduce your problem (for me, the ListBox is scrolled to the last item in the new collection when changing ItemsSource). Anyway, to scroll the ListBox to the top every time its ItemsSource changes you can use some code behind. First listen to changes in the ItemsSourceProperty and then scroll the ListBox to the top once its items has been generated
Update
Made an attached behavior that does this instead to avoid code behind. It can be used like this
<ListBox ...
behaviors:ScrollToTopBehavior.ScrollToTop="True"/>
ScrollToTopBehavior
public static class ScrollToTopBehavior
{
public static readonly DependencyProperty ScrollToTopProperty =
DependencyProperty.RegisterAttached
(
"ScrollToTop",
typeof(bool),
typeof(ScrollToTopBehavior),
new UIPropertyMetadata(false, OnScrollToTopPropertyChanged)
);
public static bool GetScrollToTop(DependencyObject obj)
{
return (bool)obj.GetValue(ScrollToTopProperty);
}
public static void SetScrollToTop(DependencyObject obj, bool value)
{
obj.SetValue(ScrollToTopProperty, value);
}
private static void OnScrollToTopPropertyChanged(DependencyObject dpo,
DependencyPropertyChangedEventArgs e)
{
ItemsControl itemsControl = dpo as ItemsControl;
if (itemsControl != null)
{
DependencyPropertyDescriptor dependencyPropertyDescriptor =
DependencyPropertyDescriptor.FromProperty(ItemsControl.ItemsSourceProperty, typeof(ItemsControl));
if (dependencyPropertyDescriptor != null)
{
if ((bool)e.NewValue == true)
{
dependencyPropertyDescriptor.AddValueChanged(itemsControl, ItemsSourceChanged);
}
else
{
dependencyPropertyDescriptor.RemoveValueChanged(itemsControl, ItemsSourceChanged);
}
}
}
}
static void ItemsSourceChanged(object sender, EventArgs e)
{
ItemsControl itemsControl = sender as ItemsControl;
EventHandler eventHandler = null;
eventHandler = new EventHandler(delegate
{
if (itemsControl.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
{
ScrollViewer scrollViewer = GetVisualChild<ScrollViewer>(itemsControl) as ScrollViewer;
scrollViewer.ScrollToTop();
itemsControl.ItemContainerGenerator.StatusChanged -= eventHandler;
}
});
itemsControl.ItemContainerGenerator.StatusChanged += eventHandler;
}
}
And an implementation of GetVisualChild
private T GetVisualChild<T>(DependencyObject parent) where T : Visual
{
T child = default(T);
int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < numVisuals; i++)
{
Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
child = v as T;
if (child == null)
{
child = GetVisualChild<T>(v);
}
if (child != null)
{
break;
}
}
return child;
}
Late answer:
A simple solution is to add an event handler for the TargetUpdated event, and set NotifyOnTargetUpdated=True on the ItemsSource binding:
<ListBox x:Name="listBox"
ItemsSource="{Binding MySource, NotifyOnTargetUpdated=True}"
TargetUpdated="ListBox_TargetUpdated"/>
and in the event handler, scroll to the top item:
private void ListBox_TargetUpdated(object sender, DataTransferEventArgs e)
{
if (listBox.Items.Count > 0)
{
listBox.ScrollIntoView(listBox.Items[0]);
}
}
Try this:
if (listBox.Items.Count > 0) {
listBox.ScrollIntoView(listBox.Items[0]);
}
Improved Fredrik Hedblad's answer to work with ObservableCollection:
public static class ItemsControlAttachedProperties
{
#region ScrollToTopOnItemsSourceChange Property
public static readonly DependencyProperty ScrollToTopOnItemsSourceChangeProperty =
DependencyProperty.RegisterAttached(
"ScrollToTopOnItemsSourceChange",
typeof(bool),
typeof(ItemsControlAttachedProperties),
new UIPropertyMetadata(false, OnScrollToTopOnItemsSourceChangePropertyChanged));
public static bool GetScrollToTopOnItemsSourceChange(DependencyObject obj)
{
return (bool) obj.GetValue(ScrollToTopOnItemsSourceChangeProperty);
}
public static void SetScrollToTopOnItemsSourceChange(DependencyObject obj, bool value)
{
obj.SetValue(ScrollToTopOnItemsSourceChangeProperty, value);
}
static void OnScrollToTopOnItemsSourceChangePropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e)
{
var itemsControl = obj as ItemsControl;
if (itemsControl == null)
{
throw new Exception("ScrollToTopOnItemsSourceChange Property must be attached to an ItemsControl based control.");
}
DependencyPropertyDescriptor descriptor =
DependencyPropertyDescriptor.FromProperty(ItemsControl.ItemsSourceProperty, typeof(ItemsControl));
if (descriptor != null)
{
if ((bool) e.NewValue)
{
descriptor.AddValueChanged(itemsControl, ItemsSourceChanged);
}
else
{
descriptor.RemoveValueChanged(itemsControl, ItemsSourceChanged);
}
}
}
static void ItemsSourceChanged(object sender, EventArgs e)
{
var itemsControl = sender as ItemsControl;
DoScrollToTop(itemsControl);
var collection = itemsControl.ItemsSource as INotifyCollectionChanged;
if (collection != null)
{
collection.CollectionChanged += (o, args) => DoScrollToTop(itemsControl);
}
}
static void DoScrollToTop(ItemsControl itemsControl)
{
EventHandler eventHandler = null;
eventHandler =
delegate
{
if (itemsControl.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
{
var scrollViewer = GetVisualChild<ScrollViewer>(itemsControl);
scrollViewer.ScrollToTop();
itemsControl.ItemContainerGenerator.StatusChanged -= eventHandler;
}
};
itemsControl.ItemContainerGenerator.StatusChanged += eventHandler;
}
static T GetVisualChild<T>(DependencyObject parent) where T : Visual
{
T child = default(T);
int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (var i = 0; i < numVisuals; i++)
{
var v = (Visual) VisualTreeHelper.GetChild(parent, i);
child = v as T ?? GetVisualChild<T>(v);
if (child != null)
{
break;
}
}
return child;
}
#endregion
}
When you format the control, you select a range of cells as the selection choices which are then listed in the list box. You also select a cell as the link to the selected choices in which a number will be displayed depending on the position of the selection in the list. 1 for first in the list, 2 for second etc. The code is quite simply:-
Range("A1")Select
Selection = 1
Change ("A1") to the cell you have linked
and change the 1 to the position in the list you want selected.
The cell reference being a link works both ways - if you change your selection, the number in the cell changes and if you change the number in the cell, the highlighted selection changes.
I need to search a WPF control hierarchy for controls that match a given name or type. How can I do this?
I combined the template format used by John Myczek and Tri Q's algorithm above to create a findChild Algorithm that can be used on any parent. Keep in mind that recursively searching a tree downwards could be a lengthy process. I've only spot-checked this on a WPF application, please comment on any errors you might find and I'll correct my code.
WPF Snoop is a useful tool in looking at the visual tree - I'd strongly recommend using it while testing or using this algorithm to check your work.
There is a small error in Tri Q's Algorithm. After the child is found, if childrenCount is > 1 and we iterate again we can overwrite the properly found child. Therefore I added a if (foundChild != null) break; into my code to deal with this condition.
/// <summary>
/// Finds a Child of a given item in the visual tree.
/// </summary>
/// <param name="parent">A direct parent of the queried item.</param>
/// <typeparam name="T">The type of the queried item.</typeparam>
/// <param name="childName">x:Name or Name of child. </param>
/// <returns>The first parent item that matches the submitted type parameter.
/// If not matching item can be found,
/// a null parent is being returned.</returns>
public static T FindChild<T>(DependencyObject parent, string childName)
where T : DependencyObject
{
// Confirm parent and childName are valid.
if (parent == null) return null;
T foundChild = null;
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
// If the child is not of the request child type child
T childType = child as T;
if (childType == null)
{
// recursively drill down the tree
foundChild = FindChild<T>(child, childName);
// If the child is found, break so we do not overwrite the found child.
if (foundChild != null) break;
}
else if (!string.IsNullOrEmpty(childName))
{
var frameworkElement = child as FrameworkElement;
// If the child's name is set for search
if (frameworkElement != null && frameworkElement.Name == childName)
{
// if the child's name is of the request name
foundChild = (T)child;
break;
}
}
else
{
// child element found.
foundChild = (T)child;
break;
}
}
return foundChild;
}
Call it like this:
TextBox foundTextBox =
UIHelper.FindChild<TextBox>(Application.Current.MainWindow, "myTextBoxName");
Note Application.Current.MainWindow can be any parent window.
You can also find an element by name using FrameworkElement.FindName(string).
Given:
<UserControl ...>
<TextBlock x:Name="myTextBlock" />
</UserControl>
In the code-behind file, you could write:
var myTextBlock = (TextBlock)this.FindName("myTextBlock");
Of course, because it's defined using x:Name, you could just reference the generated field, but perhaps you want to look it up dynamically rather than statically.
This approach is also available for templates, in which the named item appears multiple times (once per usage of the template).
You can use the VisualTreeHelper to find controls. Below is a method that uses the VisualTreeHelper to find a parent control of a specified type. You can use the VisualTreeHelper to find controls in other ways as well.
public static class UIHelper
{
/// <summary>
/// Finds a parent of a given item on the visual tree.
/// </summary>
/// <typeparam name="T">The type of the queried item.</typeparam>
/// <param name="child">A direct or indirect child of the queried item.</param>
/// <returns>The first parent item that matches the submitted type parameter.
/// If not matching item can be found, a null reference is being returned.</returns>
public static T FindVisualParent<T>(DependencyObject child)
where T : DependencyObject
{
// get parent item
DependencyObject parentObject = VisualTreeHelper.GetParent(child);
// we’ve reached the end of the tree
if (parentObject == null) return null;
// check if the parent matches the type we’re looking for
T parent = parentObject as T;
if (parent != null)
{
return parent;
}
else
{
// use recursion to proceed with next level
return FindVisualParent<T>(parentObject);
}
}
}
Call it like this:
Window owner = UIHelper.FindVisualParent<Window>(myControl);
I may be just repeating everyone else but I do have a pretty piece of code that extends the DependencyObject class with a method FindChild() that will get you the child by type and name. Just include and use.
public static class UIChildFinder
{
public static DependencyObject FindChild(this DependencyObject reference, string childName, Type childType)
{
DependencyObject foundChild = null;
if (reference != null)
{
int childrenCount = VisualTreeHelper.GetChildrenCount(reference);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(reference, i);
// If the child is not of the request child type child
if (child.GetType() != childType)
{
// recursively drill down the tree
foundChild = FindChild(child, childName, childType);
if (foundChild != null) break;
}
else if (!string.IsNullOrEmpty(childName))
{
var frameworkElement = child as FrameworkElement;
// If the child's name is set for search
if (frameworkElement != null && frameworkElement.Name == childName)
{
// if the child's name is of the request name
foundChild = child;
break;
}
}
else
{
// child element found.
foundChild = child;
break;
}
}
}
return foundChild;
}
}
Hope you find it useful.
If you want to find ALL controls of a specific type, you might be interested in this snippet too
public static IEnumerable<T> FindVisualChildren<T>(DependencyObject parent)
where T : DependencyObject
{
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
var childType = child as T;
if (childType != null)
{
yield return (T)child;
}
foreach (var other in FindVisualChildren<T>(child))
{
yield return other;
}
}
}
My extensions to the code.
Added overloads to find one child by type, by type and criteria (predicate), find all children of type which meet the criteria
the FindChildren method is an iterator in addition to being an extension method for DependencyObject
FindChildren walks logical sub-trees also. See Josh Smith's post linked in the blog post.
Source:
https://code.google.com/p/gishu-util/source/browse/#git%2FWPF%2FUtilities
Explanatory blog post :
http://madcoderspeak.blogspot.com/2010/04/wpf-find-child-control-of-specific-type.html
This will dismiss some elements - you should extend it like this in order to support a wider array of controls. For a brief discussion, have a look here
/// <summary>
/// Helper methods for UI-related tasks.
/// </summary>
public static class UIHelper
{
/// <summary>
/// Finds a parent of a given item on the visual tree.
/// </summary>
/// <typeparam name="T">The type of the queried item.</typeparam>
/// <param name="child">A direct or indirect child of the
/// queried item.</param>
/// <returns>The first parent item that matches the submitted
/// type parameter. If not matching item can be found, a null
/// reference is being returned.</returns>
public static T TryFindParent<T>(DependencyObject child)
where T : DependencyObject
{
//get parent item
DependencyObject parentObject = GetParentObject(child);
//we've reached the end of the tree
if (parentObject == null) return null;
//check if the parent matches the type we're looking for
T parent = parentObject as T;
if (parent != null)
{
return parent;
}
else
{
//use recursion to proceed with next level
return TryFindParent<T>(parentObject);
}
}
/// <summary>
/// This method is an alternative to WPF's
/// <see cref="VisualTreeHelper.GetParent"/> method, which also
/// supports content elements. Do note, that for content element,
/// this method falls back to the logical tree of the element!
/// </summary>
/// <param name="child">The item to be processed.</param>
/// <returns>The submitted item's parent, if available. Otherwise
/// null.</returns>
public static DependencyObject GetParentObject(DependencyObject child)
{
if (child == null) return null;
ContentElement contentElement = child as ContentElement;
if (contentElement != null)
{
DependencyObject parent = ContentOperations.GetParent(contentElement);
if (parent != null) return parent;
FrameworkContentElement fce = contentElement as FrameworkContentElement;
return fce != null ? fce.Parent : null;
}
//if it's not a ContentElement, rely on VisualTreeHelper
return VisualTreeHelper.GetParent(child);
}
}
I edited CrimsonX's code as it was not working with superclass types:
public static T FindChild<T>(DependencyObject depObj, string childName)
where T : DependencyObject
{
// Confirm obj is valid.
if (depObj == null) return null;
// success case
if (depObj is T && ((FrameworkElement)depObj).Name == childName)
return depObj as T;
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
{
DependencyObject child = VisualTreeHelper.GetChild(depObj, i);
//DFS
T obj = FindChild<T>(child, childName);
if (obj != null)
return obj;
}
return null;
}
Whilst I love recursion in general, it's not as efficient as iteration when programming in C#, so perhaps the following solution is neater than the one suggested by John Myczek? This searches up a hierarchy from a given control to find an ancestor control of a particular type.
public static T FindVisualAncestorOfType<T>(this DependencyObject Elt)
where T : DependencyObject
{
for (DependencyObject parent = VisualTreeHelper.GetParent(Elt);
parent != null; parent = VisualTreeHelper.GetParent(parent))
{
T result = parent as T;
if (result != null)
return result;
}
return null;
}
Call it like this to find the Window containing a control called ExampleTextBox:
Window window = ExampleTextBox.FindVisualAncestorOfType<Window>();
Here's my code to find controls by Type while controlling how deep we go into the hierarchy
(maxDepth == 0 means infinitely deep).
public static class FrameworkElementExtension
{
public static object[] FindControls(
this FrameworkElement f, Type childType, int maxDepth)
{
return RecursiveFindControls(f, childType, 1, maxDepth);
}
private static object[] RecursiveFindControls(
object o, Type childType, int depth, int maxDepth = 0)
{
List<object> list = new List<object>();
var attrs = o.GetType()
.GetCustomAttributes(typeof(ContentPropertyAttribute), true);
if (attrs != null && attrs.Length > 0)
{
string childrenProperty = (attrs[0] as ContentPropertyAttribute).Name;
foreach (var c in (IEnumerable)o.GetType()
.GetProperty(childrenProperty).GetValue(o, null))
{
if (c.GetType().FullName == childType.FullName)
list.Add(c);
if (maxDepth == 0 || depth < maxDepth)
list.AddRange(RecursiveFindControls(
c, childType, depth + 1, maxDepth));
}
}
return list.ToArray();
}
}
exciton80... I was having a problem with your code not recursing through usercontrols. It was hitting the Grid root and throwing an error. I believe this fixes it for me:
public static object[] FindControls(this FrameworkElement f, Type childType, int maxDepth)
{
return RecursiveFindControls(f, childType, 1, maxDepth);
}
private static object[] RecursiveFindControls(object o, Type childType, int depth, int maxDepth = 0)
{
List<object> list = new List<object>();
var attrs = o.GetType().GetCustomAttributes(typeof(ContentPropertyAttribute), true);
if (attrs != null && attrs.Length > 0)
{
string childrenProperty = (attrs[0] as ContentPropertyAttribute).Name;
if (String.Equals(childrenProperty, "Content") || String.Equals(childrenProperty, "Children"))
{
var collection = o.GetType().GetProperty(childrenProperty).GetValue(o, null);
if (collection is System.Windows.Controls.UIElementCollection) // snelson 6/6/11
{
foreach (var c in (IEnumerable)collection)
{
if (c.GetType().FullName == childType.FullName)
list.Add(c);
if (maxDepth == 0 || depth < maxDepth)
list.AddRange(RecursiveFindControls(
c, childType, depth + 1, maxDepth));
}
}
else if (collection != null && collection.GetType().BaseType.Name == "Panel") // snelson 6/6/11; added because was skipping control (e.g., System.Windows.Controls.Grid)
{
if (maxDepth == 0 || depth < maxDepth)
list.AddRange(RecursiveFindControls(
collection, childType, depth + 1, maxDepth));
}
}
}
return list.ToArray();
}
I have a sequence function like this (which is completely general):
public static IEnumerable<T> SelectAllRecursively<T>(this IEnumerable<T> items, Func<T, IEnumerable<T>> func)
{
return (items ?? Enumerable.Empty<T>()).SelectMany(o => new[] { o }.Concat(SelectAllRecursively(func(o), func)));
}
Getting immediate children:
public static IEnumerable<DependencyObject> FindChildren(this DependencyObject obj)
{
return Enumerable.Range(0, VisualTreeHelper.GetChildrenCount(obj))
.Select(i => VisualTreeHelper.GetChild(obj, i));
}
Finding all children down the hiararchical tree:
public static IEnumerable<DependencyObject> FindAllChildren(this DependencyObject obj)
{
return obj.FindChildren().SelectAllRecursively(o => o.FindChildren());
}
You can call this on the Window to get all controls.
After you have the collection, you can use LINQ (i.e. OfType, Where).
Since the question is general enough that it might attract people looking for answers to very trivial cases: if you just want a child rather than a descendant, you can use Linq:
private void ItemsControlItem_Loaded(object sender, RoutedEventArgs e)
{
if (SomeCondition())
{
var children = (sender as Panel).Children;
var child = (from Control child in children
where child.Name == "NameTextBox"
select child).First();
child.Focus();
}
}
or of course the obvious for loop iterating over Children.
These options already talk about traversing the Visual Tree in C#.
Its possible to traverse the visual tree in xaml as well using RelativeSource markup extension. msdn
find by type
Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type <TypeToFind>}}}"
Here is a solution that uses a flexible predicate:
public static DependencyObject FindChild(DependencyObject parent, Func<DependencyObject, bool> predicate)
{
if (parent == null) return null;
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
if (predicate(child))
{
return child;
}
else
{
var foundChild = FindChild(child, predicate);
if (foundChild != null)
return foundChild;
}
}
return null;
}
You can for example call it like this:
var child = FindChild(parent, child =>
{
var textBlock = child as TextBlock;
if (textBlock != null && textBlock.Name == "MyTextBlock")
return true;
else
return false;
}) as TextBlock;
To find an ancestor of a given type from code, you can use:
[CanBeNull]
public static T FindAncestor<T>(DependencyObject d) where T : DependencyObject
{
while (true)
{
d = VisualTreeHelper.GetParent(d);
if (d == null)
return null;
var t = d as T;
if (t != null)
return t;
}
}
This implementation uses iteration instead of recursion which can be slightly faster.
If you're using C# 7, this can be made slightly shorter:
[CanBeNull]
public static T FindAncestor<T>(DependencyObject d) where T : DependencyObject
{
while (true)
{
d = VisualTreeHelper.GetParent(d);
if (d == null)
return null;
if (d is T t)
return t;
}
}
I can't find my control with #CrimsonX or #Drew Noakes methods, because my ControlTemplate is located in a separated XAML file.
I have found the control using the following method:
private Image backImage;
private void Diagram_Loaded(object sender, System.Windows.RoutedEventArgs e)
{
// here is the example of the ControlTemplate declaration
//<ControlTemplate x:Key="DiagramControlTemplate1" TargetType="{x:Type Diagram}">
var ctrlTemplate = (ControlTemplate)FindResource("DiagramControlTemplate1");
// diagram is the x:Name of TemplatedControl and, "backImage" is the name of control that I want to find.
var imageControl = ctrlTemplate.FindName("backImage", diagram);
if (imageControl != null)
{
this.backImage = (Image)imageControl;
}
}
This is working for me.
This code just fixes #CrimsonX answer's bug:
public static T FindChild<T>(DependencyObject parent, string childName)
where T : DependencyObject
{
// Confirm parent and childName are valid.
if (parent == null) return null;
T foundChild = null;
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
// If the child is not of the request child type child
T childType = child as T;
if (childType == null)
{
// recursively drill down the tree
foundChild = FindChild<T>(child, childName);
// If the child is found, break so we do not overwrite the found child.
if (foundChild != null) break;
}
else if (!string.IsNullOrEmpty(childName))
{
var frameworkElement = child as FrameworkElement;
// If the child's name is set for search
if (frameworkElement != null && frameworkElement.Name == childName)
{
// if the child's name is of the request name
foundChild = (T)child;
break;
}
// recursively drill down the tree
foundChild = FindChild<T>(child, childName);
// If the child is found, break so we do not overwrite the found child.
if (foundChild != null) break;
else
{
// child element found.
foundChild = (T)child;
break;
}
}
return foundChild;
}
You just need to continue calling the method recursively if types are matching but names don't (this happens when you pass FrameworkElement as T). otherwise it's gonna return null and that's wrong.
Here are some methods that I use frequently..
Usage:
// Starts the search from thisUiElement (might be a UserContol, Window, etc..)
var combobox = thisUiElement.ChildOfType<ComboBox>();
var employeesListBox = thisUiElement.ChildOfName("EmployeesListBox");
// Starts the search from MainWindow to find the first DataGrid
var dataGrid = WpfUtils.ChildOfType<DataGrid>();
// Starts the search from MainWindow to find the all ListViews
List<ComboBox> allListViews = WpfUtils.ChildOfType<ListView>();
// Starts the search from MainWindow to find the element of name EmployeesComboBox
var combobox = WpfUtils.ChildOfName("EmployeesComboBox");
Implementation:
/*
using System.Collections.Generic;
using System.Windows;
using System.Windows.Media;
namespace WpfUtilities;
*/
public static class WpfUtils{
public static Window AppMainWindow =>
Application.Current?.MainWindow;
#region Find By Type
// Start the search from MainWindow, example usage: var combobox = WpfUtils.ChildOfType<ComboBox>();
public static T ChildOfType<T>() where T : DependencyObject =>
ChildOfType<T>(AppMainWindow);
/// This will return the first child of type T
public static T ChildOfType<T>(this DependencyObject parent)
where T : DependencyObject
{
if (parent == null) return null;
T child = default;
var numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (var i = 0; i < numVisuals; i++)
{
var v = VisualTreeHelper.GetChild(parent, i);
child = v as T ?? v.ChildOfType<T>();
if (child != null)
break;
}
return child;
}
// Start the search from MainWindow, example usage: List<ComboBox> comboboxes = WpfUtils.ChildOfType<ComboBox>();
public static IEnumerable<T> ChildrenOfType<T>() where T : DependencyObject =>
ChildrenOfType<T>(AppMainWindow);
/// This will not break the search when finding the first kid of type T, but it will keep searching to return all kids of type T
public static IEnumerable<T> ChildrenOfType<T>(
this DependencyObject parent) where T : DependencyObject
{
if (parent == null) yield break;
var numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (var i = 0; i < numVisuals; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
if (child is T dependencyObject)
yield return dependencyObject;
foreach (var childOfChild in child.ChildrenOfType<T>())
yield return childOfChild;
}
}
#endregion
#region Find By Name
/// If parent is null, the search will start from MainWindow, example usage: var combobox = WpfUtils.ChildOfName("EmployeesCombobox");
public static FrameworkElement ChildOfName(string childName,
DependencyObject parent = null)
{
parent ??= AppMainWindow;
object child = null;
var numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (var i = 0; i < numVisuals; i++)
{
var v = VisualTreeHelper.GetChild(parent, i);
child = v is FrameworkElement f && f.Name == childName
? f
: ChildOfName(childName, v);
if (child != null)
break;
}
return child as FrameworkElement;
}
#endregion
#region
// Yet another useful method, if you are writing code in a .xaml.cs file and you want to get the parent of a type.. example usage: this.ParentOfType<Grid>(); this.ParentOfType<UserControl>(); this.ParentOfType<Window>();
public static T ParentOfType<T>(this DependencyObject child) where T : DependencyObject
{
var parentDepObj = child;
do
{
parentDepObj = VisualTreeHelper.GetParent(parentDepObj);
if (parentDepObj is T parent) return parent;
} while (parentDepObj != null);
return null;
}
#endregion
}
I was able to find objects by name using below code.
stkMultiChildControl = stkMulti.FindChild<StackPanel>("stkMultiControl_" + couter.ToString());
Try this
<TextBlock x:Name="txtblock" FontSize="24" >Hai Welcom to this page
</TextBlock>
Code Behind
var txtblock = sender as Textblock;
txtblock.Foreground = "Red"