Develop Reference

Hiding expander when all content is collapsed

I have A WPF Datagrid that has a Collection View Source with 3 levels of grouping on it.
I have styled the datagrid to use 3 expanders such that it looks like this:
Level 1 Expander
<content>
Level 2 Expander
<content>
Level 3 Expander
<content>
Level 2 and Level 1 are just title of the groups
I have a second control that allows the user to show and hide level 3 items which works by binding the Level 3 expander to a Boolean "IsVisible" property in the object behind.
<!-- Style for groups under the top level. this is the style for how a sample is displayed -->
<GroupStyle>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Margin" Value="0,0,0,0" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type GroupItem}">
<!-- The parent control that determines whether or not an item needs to be displayed. This holds all of the sub controls displayed for a sample -->
<Expander Margin="2"
Background="{Binding Path=Name,
Converter={StaticResource SampleTypeToColourConverter}}"
IsExpanded="True"
Visibility="{Binding Path=Items[0].IsVisibleInMainScreen,
Converter={StaticResource BoolToVisibilityConverter}}">
This approach works fantasically well.
HOWEVER
If the user deselects all items in a level 3 expander, the Level 2 expander header still displays meaning that valuable real estate is used up showing the header of a group with no visible data.
What I would like is a way to bind the visibility of the level 2 expander to its child controls and say "If all children are visible then show the expander, otherwise collapse it"
Is this possible?

I found a rather simple and clean way, yet not perfect, to achieve your goal. This should do the trick if hou don't have too much groups.
I've just added this trigger to the GroupItem ControlTemplate :
<ControlTemplate.Triggers>
<DataTrigger Binding="{Binding ElementName=IP, Path=ActualHeight}" Value="0">
<Setter Property="Visibility" Value="Hidden"/>
<Setter Property="Height" Value="1"/>
</DataTrigger>
</ControlTemplate.Triggers>
When the ItemsPresenter (IP) ActualSize drops to zero, it Will almost collapse the header.
Why almost ?
When the control gets initialized and before the binding occurs, the ItemPresenter ActualHeight is 0 and when Visibility is set to Collapsed, the ItemPresenter doesn't get rendered at all.
Using Visibility.Hidden allows the ItemsPresenter to go to the render phase and be mesured.
I succedeed to drop Height to .4 px but I suspect this to be device dependant.

Assuming that you are using an MVVM sort of style, you could bind instead to a property of your group object that returns false if all of the children are invisible:
public bool AreChildrenVisible { get { return _children.Any(x=>x.IsVisibleInMainScreen); } }
Alternatively, pass the collection of Items through a Converter class to return Visibility depending on the aggregate status of all the subItems in the group.

This isn't a direct answer as you would have to implement it specifically for your needs but previously I have used a an override of the Grid Control to create dynamic grid allocation of members, if there are no visible members it then hides the parent group box.
public class DynamicLayoutGrid : Grid
{
protected override void OnInitialized(EventArgs e)
{
//Hook up the loaded event (this is used because it fires after the visibility binding has occurred)
this.Loaded += new RoutedEventHandler(DynamicLayoutGrid_Loaded);
base.OnInitialized(e);
}
void DynamicLayoutGrid_Loaded(object sender, RoutedEventArgs e)
{
int numberOfColumns = ColumnDefinitions.Count;
int columnSpan = 0;
int rowNum = 0;
int columnNum = 0;
int visibleCount = 0;
foreach (UIElement child in Children)
{
//We only want to layout visible items in the grid
if (child.Visibility != Visibility.Visible)
{
continue;
}
else
{
visibleCount++;
}
//Get the column span of the element if it is not in column 0 as we might need to take this into account
columnSpan = Grid.GetColumnSpan(child);
//set the Grid row of the element
Grid.SetRow(child, rowNum);
//set the grid column of the element (and shift it along if the previous element on this row had a rowspan greater than 0
Grid.SetColumn(child, columnNum);
//If there isn't any columnspan then just move to the next column normally
if (columnSpan == 0)
{
columnSpan = 1;
}
//Move to the next available column
columnNum += columnSpan;
//Move to the next row and start the columns again
if (columnNum >= numberOfColumns)
{
rowNum++;
columnNum = 0;
}
}
if (visibleCount == 0)
{
if (this.Parent.GetType() == typeof(GroupBox))
{
(this.Parent as GroupBox).Visibility = Visibility.Collapsed;
}
}
}
}

Use IMultiValueConverter implementation to convert items to visibility.
If all items IsVisibleInMainScreen property return true the converter will return visible else hidden.
Use the converter in the same place U used to convert the first item in original example

Create a property out of a Class

I have created a class, which shortens a text to fit into a textbox, while also adding "...".
Example:
[ThisTextis]toolong > [ThisTex...]
I'm using Microsoft Visual Studio 2013 on a Windows 8.1 VM (Virtual Machine) and the software is an App.
Now it might not be perfect, but that works all wonderful and fine. What I want to know now is if I can create a boolean property out of that class, so the user can enable/disable it on a textbox in XAML:
<TextBox CutText="True"/>
The problem is that I already use the pre-existing Text property inside the class and my code is not as beautiful as I wish it to be.
Anyways, I'd be very glad for any advice and/or help.
Edit: Simply put, I want to create a TextBlock.TextTrimming property for a TextBox, since the already existing property is restricted to TextBlock.
Here is the Class:
class CutText
{
//Create a new instance of a textbox
TextBox textCut = new TextBox();
//Reset at start
public void ResetText(TextBox text)
{
//Overwrite textCut with the chosen TextBox
textCut = text;
//Handles the possibility of already filled textbox
if (textCut.Text != "" || textCut.Text != null)
{
_text = textCut.Text;
}
//Prevents text from being 'Null'
else
{
_text = "";
}
}
//Cuts text to width of textbox
private string CutTextToWidth(string text, double fontSize, double width)
{
//boolean to check if width of text is correct
bool validArea = false;
//comply with difference in width of characters
double CharDiffLength = (stringWidth("M", fontSize) - stringWidth("|", fontSize));
//shortened text
string shortText = text;
//last length which was too long
int LastLongLen = text.Length;
//last length which fit into textbox
int LastFitLen = 0;
if (stringWidth(text, fontSize) < width)
{
shortText = text;
}
else
{
//repeat until the text fits into the appointed area
while (!validArea)
{
if (width < stringWidth(shortText, fontSize))
{
//text is still too long
LastLongLen = shortText.Length;
}
else
{
//text is not too long
LastFitLen = shortText.Length;
}
int newLen = (LastFitLen + LastLongLen) / 2;
if (shortText.Length != newLen)
{
//set shortened text
shortText = text.Substring(0, newLen) + "\u2026";
}
validArea = ((width - 10 < stringWidth(shortText, fontSize)) && (stringWidth(shortText, fontSize) < width));
}
}
//return the shortened text
return shortText;
}
//Calculate the width of the text
private double stringWidth(string s, double fontSize)
{
if (s == " ")
s = "\u00a0";
TextBlock t = new TextBlock()
{
FontSize = fontSize,
Text = s
};
t.Measure(new Size(double.MaxValue, double.MaxValue));
return t.ActualWidth;
}
//(GotFocus) Replaces cut text with full text and places the cursor at the chosen position
public void GotFocusText()
{
int index = textCut.SelectionStart;
textCut.Text = _text;
textCut.SelectionStart = index;
}
//(LostFocus) Saves cut text into property / empties the textbox if nothing has been written and sets tooltip
public void LostFocusText()
{
if (!string.IsNullOrWhiteSpace(textCut.Text))
{
Text = textCut.Text;
}
else
{
Text = "";
}
ToolTipService.SetToolTip(textCut, _text);
}
//TextBox.Text Property
private string _text;
public string Text
{
get { return _text; }
set
{
_text = value;
//Receive text, fontsize and width of textbox
textCut.Text = CutTextToWidth(_text, textCut.FontSize, textCut.Width - 25);
}
}
}

I am sorry to inform you that you have wasted your time. WPF already has that functionality built in. You can set the TextBlock.TextTrimming property to CharacterEllipsis or WordEllipsis and that will automatically trim the overflowing text of the control and add the ellipsis (...). See this simple example:
<TextBlock TextTrimming="CharacterEllipsis" Width="150">
Lorem ipsum dolor sit amet, consectetur adipisicing</TextBlock>
From the TextTrimming Enumeration page on MSDN:
CharacterEllipsis: Text is trimmed at a character boundary. An ellipsis (...) is drawn in place of remaining text.
WordEllipsis: Text is trimmed at a word boundary. An ellipsis (...) is drawn in place of remaining text.
UPDATE >>>
To answer your question more directly, you should create your code in an Attached Property. That way, you could define a bool Attached Property to use the ellipsis, eg. something like this:
<TextBox TextBoxProperties.CutText="True" />
... where TextBoxProperties would be the name of the class that defines the Attached Property and CutText would be the name of the property itself. See the How to create an Attached Property section from the linked page to find out how to do that. You could use your CutText class from that property.

Using the suggestions from the other answers, I have composed a Custom Control which should be useful for you.
public class TrimmedTextBox : TextBox
{
public bool Trim
{
get { return (bool)GetValue(TrimProperty); }
set { SetValue(TrimProperty, value); }
}
// Using a DependencyProperty as the backing store for Trim. This enables animation, styling, binding, etc...
public static readonly DependencyProperty TrimProperty =
DependencyProperty.Register("Trim", typeof(bool), typeof(TrimmedTextBox), new PropertyMetadata(true));
public TextTrimming Trimming
{
get { return (TextTrimming)GetValue(TrimmingProperty); }
set { SetValue(TrimmingProperty, value); }
}
// Using a DependencyProperty as the backing store for Trimming. This enables animation, styling, binding, etc...
public static readonly DependencyProperty TrimmingProperty =
DependencyProperty.Register("Trimming", typeof(TextTrimming), typeof(TrimmedTextBox), new PropertyMetadata(TextTrimming.CharacterEllipsis));
static TrimmedTextBox()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(TrimmedTextBox), new FrameworkPropertyMetadata(typeof(TrimmedTextBox)));
}
}
And the Style:
<Style TargetType="{x:Type local:TrimmedTextBox}"
BasedOn="{StaticResource {x:Type TextBox}}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type local:TrimmedTextBox}">
<Border Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}">
<ScrollViewer x:Name="PART_ContentHost"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsKeyboardFocused" Value="False"/>
<Condition Property="Trim" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TextBox">
<Border Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}">
<TextBlock Text="{TemplateBinding Text}"
TextTrimming="{Binding Trimming, RelativeSource={RelativeSource TemplatedParent}}"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</MultiTrigger>
</Style.Triggers>
</Style>
Usage:
<local:TrimmedTextBox Trim="True"
Text="Le toucan has arrived"
Width="50"
Trimming="CharacterEllipsis"/>
You may have to play around with the style to get the desired look and feel, but the idea remains. This is a Control Template which extends TextBox, which will allow you to set whether you want the textbox to trim the contents and also what type of trimming you need.
For more information on Custom Controls, see here.

It's neither possible, nor necessary to do what you are trying to do. You cannot add new properties to existing components like that. Also, if you check out this answer to another question, there's a simpler way to achieve what you want to do by defining a WPF style for TextBox.

How to set background of a datagrid cell during AutoGeneratingColumn event depending on its value?

I'm still fighting with manipulation of cell backgrounds so I'm asking a new question.
A user "H.B." wrote that I can actually set the cell style during the AutoGeneratingColumn event - Change DataGrid cell colour based on values. The problem is that I'm not sure how to do it.
What I want:
Set different background colours for each cell depending on its value. If the value is null I also want it not to be clickable (focusable I guess).
What I have / I'm trying to do:
private void mydatagrid_AutoGeneratingColumn(object sender, DataGridAutoGeneratingColumnEventArgs e)
{
foreach (Cell cell in e.Column)
{
if (cell.Value < 1)
{
cell.Background = Color.Black;
cell.isFocusable = false;
}
else
{
cell.Background = Color.Pink;
}
}
}
This is just the pseudocode. Is something like this is possible during column auto-generation and if so, how can I edit my code so it will be valid?
I read about value convertors but I want to know if it's somehow possible programmatically, without writing XAML.
Please understand that I'm still a beginner to C#/WPF/DataGrid.
Solution part1:
I used the answer I accepted. Just put it into
<Window.Resources>
<local:ValueColorConverter x:Key="colorConverter"/>
<Style x:Key="DataGridCellStyle1" TargetType="{x:Type DataGridCell}">
<Setter Property="Padding" Value="5"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type DataGridCell}">
<Border Padding="{TemplateBinding Padding}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" SnapsToDevicePixels="True">
<Border.Background>
<MultiBinding Converter="{StaticResource colorConverter}">
<Binding RelativeSource="{RelativeSource AncestorType=DataGridCell}" Path="Content.Text"/>
<Binding RelativeSource="{RelativeSource AncestorType=DataGridCell}" Path="IsSelected"/>
</MultiBinding>
</Border.Background>
<ContentPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
And made for it a MultiBinding convertor so I can also set the background color for selected cells.
Problem:
Now I only have to solve the problem of setting focus of empty cells. Any hints?
<Style.Triggers>
<Trigger Property="HasContent" Value="False">
<Setter Property="Focusable" Value="False"/>
</Trigger>
</Style.Triggers>
This doesn't work. I had empty strings in the empty cells, but they are filled with ´null´s so it should work, right? Or what am I doing wrong :| ?
Solution part 2:
So the code above won't work as long as the cell value is a ´TextBox´ so I decided to find another way to deal with it which can be found in my answer here: https://stackoverflow.com/a/16673602/2296407
Thanks for trying to help me :)

I can propose two different solutions for your question: the first is "code-behind-style" (which you are asking for but personally I think it is not right approach in WPF) and more WPF-style (which more tricky but keeps code-behind clean and utilizes styles, triggers and converters)
Solution 1. Event handling and code-behind logic for coloring
First of all, the approach you've chosen will not work directly - the AutoGeneratingColumn event is meant to be used for altering the entire column appearance, not on the cell-by-cell basis. So it can be used for, say, attaching the correct style to entire column basing on it's display index or bound property.
Generally speaking, for the first time the event is raised your datagrid will not have any rows (and consequently - cells) at all. If you really need to catch the event - consider your DataGrid.LoadingRow event instead. And you will not be able to get the cells that easy :)
So, what you do: handle the LoadingRow event, get the row (it has the Item property which holds (surprisingly :)) your bound item), get the bound item, make all needed calculations, get the cell you need to alter and finally alter the style of the target cell.
Here is the code (as item I use a sample object with the int "Value" property that I use for coloring).
XAML
<DataGrid Name="mygrid" ItemsSource="{Binding Items}" AutoGenerateColumns="True" LoadingRow="DataGrid_OnLoadingRow"/>
.CS
private void DataGrid_OnLoadingRow(object sender, DataGridRowEventArgs e)
{
Dispatcher.BeginInvoke(DispatcherPriority.Render, new Action(() => AlterRow(e)));
}
private void AlterRow(DataGridRowEventArgs e)
{
var cell = GetCell(mygrid, e.Row, 1);
if (cell == null) return;
var item = e.Row.Item as SampleObject;
if (item == null) return;
var value = item.Value;
if (value <= 1) cell.Background = Brushes.Red;
else if (value <= 2) cell.Background = Brushes.Yellow;
else cell.Background = Brushes.Green;
}
public static DataGridRow GetRow(DataGrid grid, int index)
{
var row = grid.ItemContainerGenerator.ContainerFromIndex(index) as DataGridRow;
if (row == null)
{
// may be virtualized, bring into view and try again
grid.ScrollIntoView(grid.Items[index]);
row = (DataGridRow)grid.ItemContainerGenerator.ContainerFromIndex(index);
}
return row;
}
public 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++)
{
var v = (Visual)VisualTreeHelper.GetChild(parent, i);
child = v as T ?? GetVisualChild<T>(v);
if (child != null)
{
break;
}
}
return child;
}
public static DataGridCell GetCell(DataGrid host, DataGridRow row, int columnIndex)
{
if (row == null) return null;
var presenter = GetVisualChild<DataGridCellsPresenter>(row);
if (presenter == null) return null;
// try to get the cell but it may possibly be virtualized
var cell = (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(columnIndex);
if (cell == null)
{
// now try to bring into view and retreive the cell
host.ScrollIntoView(row, host.Columns[columnIndex]);
cell = (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(columnIndex);
}
return cell;
}
Solution 2. WPF-style
This solution uses code-behind only for value-to-color convertions (assuming that that logic of coloring is more complex than equality comparison - in that case you can use triggers and do not mess with converters).
What you do: set DataGrid.CellStyle property with style that contains a data trigger, which checks if the cell is within a desired column (basing on it's DisplayIndex) and if it is - applies background through a converter.
XAML
<DataGrid Name="mygrid" ItemsSource="{Binding Items}" AutoGenerateColumns="True">
<DataGrid.Resources>
<local:ValueColorConverter x:Key="colorconverter"/>
</DataGrid.Resources>
<DataGrid.CellStyle>
<Style TargetType="DataGridCell">
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Column.DisplayIndex}" Value="1">
<Setter Property="Background" Value="{Binding RelativeSource={RelativeSource Self}, Path=Content.Text, Converter={StaticResource colorconverter}}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</DataGrid.CellStyle>
</DataGrid>
.CS
public class ValueColorConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var str = value as string;
if (str == null) return null;
int intValue;
if (!int.TryParse(str, out intValue)) return null;
if (intValue <= 1) return Brushes.Red;
else if (intValue <= 2) return Brushes.Yellow;
else return Brushes.Green;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
UPD: If you need to color entire datagrid, XAML is much easier (no need to use triggers). Use the following CellStyle:
<DataGrid.CellStyle>
<Style TargetType="DataGridCell">
<Setter Property="Background" Value="{Binding RelativeSource={RelativeSource Self}, Path=Content.Text, Converter={StaticResource colorconverter}}"/>
</Style>
</DataGrid.CellStyle>

What i meant is that you can set the CellStyle property of the column, you can not manipulate cells directly as they are not available in this event. The style can contain your conditional logic in the form of DataTriggers (will need a converter as you have "less-than" and not equals) and Setters.
Also if the logic is not specific to the columns you can set the style globally on the grid itself. The point of using the event would be to manipulate the column properties which you can not access otherwise.

I am not sure whether this property (Cell.Style) is available in your WPF Datagrid. Probably some alternative exists in your case. It has worked for WinForms datagrid.
cell.Style.BackColor = System.Drawing.Color.Black;

Scrolling to an element of a virtualising ItemsControl

I have a ItemsControl which displays its items in a ScrollViewer, and does virtualisation. I am trying to scroll that ScrollViewer to an (offscreen, hence virtualised) item it contains. However, since the item is virtualised, it doesn't really exist on the screen and has no position (IIUC).
I have tried BringIntoView on the child element, but it doesn't scroll into view. I have also tried manually doing it with TransformToAncestor, TransformBounds and ScrollToVerticalOffset, but TransformToAncestor never returns (I guess also because of the virtualisation, because it has no position, but I have no proof of that) and code after it never executes.
Is it possible to scroll to an item with a virtualising ItemsControl? If so, how?

I've been looking at getting a ItemsControl with a VirtualizingStackPanel to scroll to an item for a while now, and kept finding the "use a ListBox" answer. I didn't want to, so I found a way to do it. First you need to setup a control template for your ItemsControl that has a ScrollViewer in it (which you probably already have if you're using an items control). My basic template looks like the following (contained in a handy style for the ItemsControl)
<Style x:Key="TheItemsControlStyle" TargetType="{x:Type ItemsControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ItemsControl}">
<Border BorderThickness="{TemplateBinding Border.BorderThickness}" Padding="{TemplateBinding Control.Padding}" BorderBrush="{TemplateBinding Border.BorderBrush}" Background="{TemplateBinding Panel.Background}" SnapsToDevicePixels="True">
<ScrollViewer Padding="{TemplateBinding Control.Padding}" Focusable="False" HorizontalScrollBarVisibility="Auto">
<ItemsPresenter SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}" />
</ScrollViewer>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
So I've basically got a border with a scroll viewer thats going to contain my content.
My ItemsControl is defined with:
<ItemsControl x:Name="myItemsControl" [..snip..] Style="{DynamicResource TheItemsControlStyle}" ScrollViewer.CanContentScroll="True" VirtualizingStackPanel.IsVirtualizing="True">
Ok now for the fun part. I've created a extension method to attach to any ItemsControl to get it to scroll to the given item:
public static void VirtualizedScrollIntoView(this ItemsControl control, object item) {
try {
// this is basically getting a reference to the ScrollViewer defined in the ItemsControl's style (identified above).
// you *could* enumerate over the ItemsControl's children until you hit a scroll viewer, but this is quick and
// dirty!
// First 0 in the GetChild returns the Border from the ControlTemplate, and the second 0 gets the ScrollViewer from
// the Border.
ScrollViewer sv = VisualTreeHelper.GetChild(VisualTreeHelper.GetChild((DependencyObject)control, 0), 0) as ScrollViewer;
// now get the index of the item your passing in
int index = control.Items.IndexOf(item);
if(index != -1) {
// since the scroll viewer is using content scrolling not pixel based scrolling we just tell it to scroll to the index of the item
// and viola! we scroll there!
sv.ScrollToVerticalOffset(index);
}
} catch(Exception ex) {
Debug.WriteLine("What the..." + ex.Message);
}
}
So with the extension method in place you would use it just like ListBox's companion method:
myItemsControl.VirtualizedScrollIntoView(someItemInTheList);
Works great!
Note that you can also call sv.ScrollToEnd() and the other usual scrolling methods to get around your items.

Poking around in the .NET source code leads me to recommend you the use of a ListBox and its ScrollIntoView method. The implementation of this method relies on a few internal methods like VirtualizingPanel.BringIndexIntoView which forces the creation of the item at that index and scrolls to it. The fact that many of those mechanism are internal means that if you try to do this on your own you're gonna have a bad time.
(To make the selection this brings with it invisible you can retemplate the ListBoxItems)

I know this is an old thread, but in case someone else (like me) comes across it, I figured it would be worth an updated answer that I just discovered.
As of .NET Framework 4.5, VirtualizingPanel has a public BringIndexIntoViewPublic method which works like a charm, including with pixel based scrolling. You'll have to either sub-class your ItemsControl, or use the VisualTreeHelper to find its child VirtualizingPanel, but either way it's now very easy to force your ItemsControl to scroll precisely to a particular item/index.

Using #AaronCook example, Created a behavior that works for my VirtualizingItemsControl. Here is the code for that:
public class ItemsControlScrollToSelectedBehavior : Behavior<ItemsControl>
{
public static readonly DependencyProperty SelectedItemProperty =
DependencyProperty.Register("SelectedItem", typeof(object), typeof(ItemsControlScrollToSelectedBehavior),
new FrameworkPropertyMetadata(null,
new PropertyChangedCallback(OnSelectedItemsChanged)));
public object SelectedItem
{
get => GetValue(SelectedItemProperty);
set => SetValue(SelectedItemProperty, value);
}
private static void OnSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
ItemsControlScrollToSelectedBehavior target = (ItemsControlScrollToSelectedBehavior)d;
object oldSelectedItems = e.OldValue;
object newSelectedItems = target.SelectedItem;
target.OnSelectedItemsChanged(oldSelectedItems, newSelectedItems);
}
protected virtual void OnSelectedItemsChanged(object oldSelectedItems, object newSelectedItems)
{
try
{
var sv = VisualTreeHelper.GetChild(VisualTreeHelper.GetChild(AssociatedObject, 0), 0) as ScrollViewer;
// now get the index of the item your passing in
int index = AssociatedObject.Items.IndexOf(newSelectedItems);
if (index != -1)
{
sv?.ScrollToVerticalOffset(index);
}
}
catch
{
// Ignore
}
}
}
and usage is:
<ItemsControl Style="{StaticResource VirtualizingItemsControl}"
ItemsSource="{Binding BoundItems}">
<i:Interaction.Behaviors>
<behaviors:ItemsControlScrollToSelectedBehavior SelectedItem="{Binding SelectedItem}" />
</i:Interaction.Behaviors>
</ItemsControl>
Helpful for those who like Behaviors and clean XAML, no code-behind.

I know I'm pretty late to the party but hopefully this may help someone else coming along looking for the solution...
int index = myItemsControl.Items.IndexOf(*your item*).FirstOrDefault();
int rowHeight = *height of your rows*;
myScrollView.ScrollToVerticalOffset(index*rowHeight);
//this will bring the given item to the top of the scrollViewer window
... and my XAML is setup like this...
<ScrollViewer x:Name="myScrollView">
<ItemsControl x:Name="myItemsControl">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<!-- data here -->
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</ScrollViewer>

This is an old thread, but I would like to suggest one way:
/// <summary>
/// Scrolls to the desired item
/// </summary>
/// <param name="control">ItemsControl</param>
/// <param name="item">item</param>
public static void ScrollIntoView(this ItemsControl control, Object item)
{
FrameworkElement framework = control.ItemContainerGenerator.ContainerFromItem(item) as FrameworkElement;
if (framework == null) { return; }
framework.BringIntoView();
}

Can't access to the content of a ControlTemplate from code behind

Here is my XAML. The UserControl is named "Event"
<UserControl.Resources>
<Style x:Key="eventStyle" TargetType="Thumb">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Thumb}">
<Rectangle Name="rect" Fill="CadetBlue" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</UserControl.Resources>
<Canvas>
<Thumb Canvas.Left="0" Canvas.Top="0" Name="MoveThumb" Style="{StaticResource eventStyle}" Cursor="SizeAll" DragDelta="MoveThumb_DragDelta" DragStarted="MoveThumb_DragStarted" DragCompleted="MoveThumb_DragCompleted" />
</Canvas>
And here is the code behind
var ev = new Event();
var rect = ev.Template.FindName("rect", ev) as Rectangle;
But it doesn't work : the "rect" variable is null. What am I doing wrong ?
Thanks

The template you're defining is applied to the Thumb control, and not the Event control - that's why there's no rect control in Event's template.
Since you're creating the Event control from another class, what you can do is expose the MoveThumb control as a property in Event's code-behind, like this:
public Thumb TheThumb
{
get { return MoveThumb; }
}
Then you can change your code to this:
var ev = new Event();
var rect = ev.TheThumb.Template.FindName("rect", ev.TheThumb) as Rectangle;
Better yet, you can expose the rect control as a property:
public Rectangle Rect
{
get { return MoveThumb.Template.FindName("rect", MoveThumb) as Rectangle; }
}
and use it like this
var ev = new Event();
var rect = ev.Rect;

It returned null because the function FindName("controlName",TemplatedParent) expects a control on which the template is applied as the second parameter. From the code you've provided, I couldn't see when the template was applied to the control (ev used to the default template). Hence, the rect variable was null.
Try this
var rectangle = MoveThumb.Template.FindName("rect", MoveThumb) as Rectangle;
More information is available here and here