I want to include an AvalonEdit TextEditor control into my MVVM application. The first thing I require is to be able to bind to the TextEditor.Text property so that I can display text. To do this I have followed and example that was given in Making AvalonEdit MVVM compatible. Now, I have implemented the following class using the accepted answer as a template
public sealed class MvvmTextEditor : TextEditor, INotifyPropertyChanged
{
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(string), typeof(MvvmTextEditor),
new PropertyMetadata((obj, args) =>
{
MvvmTextEditor target = (MvvmTextEditor)obj;
target.Text = (string)args.NewValue;
})
);
public new string Text
{
get { return base.Text; }
set { base.Text = value; }
}
protected override void OnTextChanged(EventArgs e)
{
RaisePropertyChanged("Text");
base.OnTextChanged(e);
}
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged(string info)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
Where the XAML is
<Controls:MvvmTextEditor HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
FontFamily="Consolas"
FontSize="9pt"
Margin="2,2"
Text="{Binding Text, NotifyOnSourceUpdated=True, Mode=TwoWay}"/>
Firstly, this does not work. The Binding is not shown in Snoop at all (not red, not anything, in fact I cannot even see the Text dependency property).
I have seen this question which is exactly the same as mine Two-way binding in AvalonEdit doesn't work but the accepted answer does not work (at least for me). So my question is:
How can I perform two way binding using the above method and what is the correct implementation of my MvvmTextEditor class?
Thanks for your time.
Note: I have my Text property in my ViewModel and it implements the required INotifyPropertyChanged interface.
Create a Behavior class that will attach the TextChanged event and will hook up the dependency property that is bound to the ViewModel.
AvalonTextBehavior.cs
public sealed class AvalonEditBehaviour : Behavior<TextEditor>
{
public static readonly DependencyProperty GiveMeTheTextProperty =
DependencyProperty.Register("GiveMeTheText", typeof(string), typeof(AvalonEditBehaviour),
new FrameworkPropertyMetadata(default(string), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, PropertyChangedCallback));
public string GiveMeTheText
{
get { return (string)GetValue(GiveMeTheTextProperty); }
set { SetValue(GiveMeTheTextProperty, value); }
}
protected override void OnAttached()
{
base.OnAttached();
if (AssociatedObject != null)
AssociatedObject.TextChanged += AssociatedObjectOnTextChanged;
}
protected override void OnDetaching()
{
base.OnDetaching();
if (AssociatedObject != null)
AssociatedObject.TextChanged -= AssociatedObjectOnTextChanged;
}
private void AssociatedObjectOnTextChanged(object sender, EventArgs eventArgs)
{
var textEditor = sender as TextEditor;
if (textEditor != null)
{
if (textEditor.Document != null)
GiveMeTheText = textEditor.Document.Text;
}
}
private static void PropertyChangedCallback(
DependencyObject dependencyObject,
DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
var behavior = dependencyObject as AvalonEditBehaviour;
if (behavior.AssociatedObject!= null)
{
var editor = behavior.AssociatedObject as TextEditor;
if (editor.Document != null)
{
var caretOffset = editor.CaretOffset;
editor.Document.Text = dependencyPropertyChangedEventArgs.NewValue.ToString();
editor.CaretOffset = caretOffset;
}
}
}
}
View.xaml
<avalonedit:TextEditor
WordWrap="True"
ShowLineNumbers="True"
LineNumbersForeground="Magenta"
x:Name="textEditor"
FontFamily="Consolas"
SyntaxHighlighting="XML"
FontSize="10pt">
<i:Interaction.Behaviors>
<controls:AvalonEditBehaviour GiveMeTheText="{Binding Test, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</i:Interaction.Behaviors>
</avalonedit:TextEditor>
i must be defined as
xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"
ViewModel.cs
private string _test;
public string Test
{
get { return _test; }
set { _test = value; }
}
That should give you the Text and push it back to the ViewModel.
Create a BindableAvalonEditor class with a two-way binding on the Text property.
I was able to establish a two-way binding with the latest version of AvalonEdit by combining Jonathan Perry's answer and 123 456 789 0's answer. This allows a direct two-way binding without the need for behaviors.
Here is the source code...
public class BindableAvalonEditor : ICSharpCode.AvalonEdit.TextEditor, INotifyPropertyChanged
{
/// <summary>
/// A bindable Text property
/// </summary>
public new string Text
{
get
{
return (string)GetValue(TextProperty);
}
set
{
SetValue(TextProperty, value);
RaisePropertyChanged("Text");
}
}
/// <summary>
/// The bindable text property dependency property
/// </summary>
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register(
"Text",
typeof(string),
typeof(BindableAvalonEditor),
new FrameworkPropertyMetadata
{
DefaultValue = default(string),
BindsTwoWayByDefault = true,
PropertyChangedCallback = OnDependencyPropertyChanged
}
);
protected static void OnDependencyPropertyChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args)
{
var target = (BindableAvalonEditor)obj;
if (target.Document != null)
{
var caretOffset = target.CaretOffset;
var newValue = args.NewValue;
if (newValue == null)
{
newValue = "";
}
target.Document.Text = (string)newValue;
target.CaretOffset = Math.Min(caretOffset, newValue.ToString().Length);
}
}
protected override void OnTextChanged(EventArgs e)
{
if (this.Document != null)
{
Text = this.Document.Text;
}
base.OnTextChanged(e);
}
/// <summary>
/// Raises a property changed event
/// </summary>
/// <param name="property">The name of the property that updates</param>
public void RaisePropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
I like none of these solutions. The reason the author didn't create a dependency property on Text is for performance reason. Working around it by creating an attached property means the text string must be recreated on every key stroke. On a 100mb file, this can be a serious performance issue. Internally, it only uses a document buffer and will never create the full string unless requested.
It exposes another property, Document, which is a dependency property, and it exposes the Text property to construct the string only when needed. Although you can bind to it, it would mean designing your ViewModel around a UI element which defeats the purpose of having a ViewModel UI-agnostic. I don't like that option either.
Honestly, the cleanest(ish) solution is to create 2 events in your ViewModel, one to display the text and one to update the text. Then you write a one-line event handler in your code-behind, which is fine since it's purely UI-related. That way, you construct and assign the full document string only when it's truly needed. Additionally, you don't even need to store (nor update) the text in the ViewModel. Just raise DisplayScript and UpdateScript when it is needed.
It's not an ideal solution, but there are less drawbacks than any other method I've seen.
TextBox also faces a similar issue, and it solves it by internally using a DeferredReference object that constructs the string only when it is really needed. That class is internal and not available to the public, and the Binding code is hard-coded to handle DeferredReference in a special way. Unfortunately there doesn't seen to be any way of solving the problem in the same way as TextBox -- perhaps unless TextEditor would inherit from TextBox.
Another nice OOP approach is to download the source code of AvalonEdit (it's open sourced), and creating a new class that inherits from TextEditor class (the main editor of AvalonEdit).
What you want to do is basically override the Text property and implement an INotifyPropertyChanged version of it, using dependency property for the Text property and raising the OnPropertyChanged event when text is changed (this can be done by overriding the OnTextChanged() method.
Here's a quick code (fully working) example that works for me:
public class BindableTextEditor : TextEditor, INotifyPropertyChanged
{
/// <summary>
/// A bindable Text property
/// </summary>
public new string Text
{
get { return base.Text; }
set { base.Text = value; }
}
/// <summary>
/// The bindable text property dependency property
/// </summary>
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(string), typeof(BindableTextEditor), new PropertyMetadata((obj, args) =>
{
var target = (BindableTextEditor)obj;
target.Text = (string)args.NewValue;
}));
protected override void OnTextChanged(EventArgs e)
{
RaisePropertyChanged("Text");
base.OnTextChanged(e);
}
/// <summary>
/// Raises a property changed event
/// </summary>
/// <param name="property">The name of the property that updates</param>
public void RaisePropertyChanged(string property)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(property));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
For those wondering about an MVVM implementation using AvalonEdit, here is one of the ways it can be done, first we have the class
/// <summary>
/// Class that inherits from the AvalonEdit TextEditor control to
/// enable MVVM interaction.
/// </summary>
public class CodeEditor : TextEditor, INotifyPropertyChanged
{
// Vars.
private static bool canScroll = true;
/// <summary>
/// Default constructor to set up event handlers.
/// </summary>
public CodeEditor()
{
// Default options.
FontSize = 12;
FontFamily = new FontFamily("Consolas");
Options = new TextEditorOptions
{
IndentationSize = 3,
ConvertTabsToSpaces = true
};
}
#region Text.
/// <summary>
/// Dependancy property for the editor text property binding.
/// </summary>
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(string), typeof(CodeEditor),
new PropertyMetadata((obj, args) =>
{
CodeEditor target = (CodeEditor)obj;
target.Text = (string)args.NewValue;
}));
/// <summary>
/// Provide access to the Text.
/// </summary>
public new string Text
{
get { return base.Text; }
set { base.Text = value; }
}
/// <summary>
/// Return the current text length.
/// </summary>
public int Length
{
get { return base.Text.Length; }
}
/// <summary>
/// Override of OnTextChanged event.
/// </summary>
protected override void OnTextChanged(EventArgs e)
{
RaisePropertyChanged("Length");
base.OnTextChanged(e);
}
/// <summary>
/// Event handler to update properties based upon the selection changed event.
/// </summary>
void TextArea_SelectionChanged(object sender, EventArgs e)
{
this.SelectionStart = SelectionStart;
this.SelectionLength = SelectionLength;
}
/// <summary>
/// Event that handles when the caret changes.
/// </summary>
void TextArea_CaretPositionChanged(object sender, EventArgs e)
{
try
{
canScroll = false;
this.TextLocation = TextLocation;
}
finally
{
canScroll = true;
}
}
#endregion // Text.
#region Caret Offset.
/// <summary>
/// DependencyProperty for the TextEditorCaretOffset binding.
/// </summary>
public static DependencyProperty CaretOffsetProperty =
DependencyProperty.Register("CaretOffset", typeof(int), typeof(CodeEditor),
new PropertyMetadata((obj, args) =>
{
CodeEditor target = (CodeEditor)obj;
if (target.CaretOffset != (int)args.NewValue)
target.CaretOffset = (int)args.NewValue;
}));
/// <summary>
/// Access to the SelectionStart property.
/// </summary>
public new int CaretOffset
{
get { return base.CaretOffset; }
set { SetValue(CaretOffsetProperty, value); }
}
#endregion // Caret Offset.
#region Selection.
/// <summary>
/// DependencyProperty for the TextLocation. Setting this value
/// will scroll the TextEditor to the desired TextLocation.
/// </summary>
public static readonly DependencyProperty TextLocationProperty =
DependencyProperty.Register("TextLocation", typeof(TextLocation), typeof(CodeEditor),
new PropertyMetadata((obj, args) =>
{
CodeEditor target = (CodeEditor)obj;
TextLocation loc = (TextLocation)args.NewValue;
if (canScroll)
target.ScrollTo(loc.Line, loc.Column);
}));
/// <summary>
/// Get or set the TextLocation. Setting will scroll to that location.
/// </summary>
public TextLocation TextLocation
{
get { return base.Document.GetLocation(SelectionStart); }
set { SetValue(TextLocationProperty, value); }
}
/// <summary>
/// DependencyProperty for the TextEditor SelectionLength property.
/// </summary>
public static readonly DependencyProperty SelectionLengthProperty =
DependencyProperty.Register("SelectionLength", typeof(int), typeof(CodeEditor),
new PropertyMetadata((obj, args) =>
{
CodeEditor target = (CodeEditor)obj;
if (target.SelectionLength != (int)args.NewValue)
{
target.SelectionLength = (int)args.NewValue;
target.Select(target.SelectionStart, (int)args.NewValue);
}
}));
/// <summary>
/// Access to the SelectionLength property.
/// </summary>
public new int SelectionLength
{
get { return base.SelectionLength; }
set { SetValue(SelectionLengthProperty, value); }
}
/// <summary>
/// DependencyProperty for the TextEditor SelectionStart property.
/// </summary>
public static readonly DependencyProperty SelectionStartProperty =
DependencyProperty.Register("SelectionStart", typeof(int), typeof(CodeEditor),
new PropertyMetadata((obj, args) =>
{
CodeEditor target = (CodeEditor)obj;
if (target.SelectionStart != (int)args.NewValue)
{
target.SelectionStart = (int)args.NewValue;
target.Select((int)args.NewValue, target.SelectionLength);
}
}));
/// <summary>
/// Access to the SelectionStart property.
/// </summary>
public new int SelectionStart
{
get { return base.SelectionStart; }
set { SetValue(SelectionStartProperty, value); }
}
#endregion // Selection.
#region Properties.
/// <summary>
/// The currently loaded file name. This is bound to the ViewModel
/// consuming the editor control.
/// </summary>
public string FilePath
{
get { return (string)GetValue(FilePathProperty); }
set { SetValue(FilePathProperty, value); }
}
// Using a DependencyProperty as the backing store for FilePath.
// This enables animation, styling, binding, etc...
public static readonly DependencyProperty FilePathProperty =
DependencyProperty.Register("FilePath", typeof(string), typeof(CodeEditor),
new PropertyMetadata(String.Empty, OnFilePathChanged));
#endregion // Properties.
#region Raise Property Changed.
/// <summary>
/// Implement the INotifyPropertyChanged event handler.
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
public void RaisePropertyChanged([CallerMemberName] string caller = null)
{
var handler = PropertyChanged;
if (handler != null)
PropertyChanged(this, new PropertyChangedEventArgs(caller));
}
#endregion // Raise Property Changed.
}
Then in your view where you want to have AvalonEdit, you can do
...
<Grid>
<Local:CodeEditor
x:Name="CodeEditor"
FilePath="{Binding FilePath,
Mode=TwoWay,
NotifyOnSourceUpdated=True,
NotifyOnTargetUpdated=True}"
WordWrap="{Binding WordWrap,
Mode=TwoWay,
NotifyOnSourceUpdated=True,
NotifyOnTargetUpdated=True}"
ShowLineNumbers="{Binding ShowLineNumbers,
Mode=TwoWay,
NotifyOnSourceUpdated=True,
NotifyOnTargetUpdated=True}"
SelectionLength="{Binding SelectionLength,
Mode=TwoWay,
NotifyOnSourceUpdated=True,
NotifyOnTargetUpdated=True}"
SelectionStart="{Binding SelectionStart,
Mode=TwoWay,
NotifyOnSourceUpdated=True,
NotifyOnTargetUpdated=True}"
TextLocation="{Binding TextLocation,
Mode=TwoWay,
NotifyOnSourceUpdated=True,
NotifyOnTargetUpdated=True}"/>
</Grid>
Where this can be placed in a UserControl or Window or what ever, then in the ViewModel for this view we have (where I am using Caliburn Micro for the MVVM framework stuff)
public string FilePath
{
get { return filePath; }
set
{
if (filePath == value)
return;
filePath = value;
NotifyOfPropertyChange(() => FilePath);
}
}
/// <summary>
/// Should wrap?
/// </summary>
public bool WordWrap
{
get { return wordWrap; }
set
{
if (wordWrap == value)
return;
wordWrap = value;
NotifyOfPropertyChange(() => WordWrap);
}
}
/// <summary>
/// Display line numbers?
/// </summary>
public bool ShowLineNumbers
{
get { return showLineNumbers; }
set
{
if (showLineNumbers == value)
return;
showLineNumbers = value;
NotifyOfPropertyChange(() => ShowLineNumbers);
}
}
/// <summary>
/// Hold the start of the currently selected text.
/// </summary>
private int selectionStart = 0;
public int SelectionStart
{
get { return selectionStart; }
set
{
selectionStart = value;
NotifyOfPropertyChange(() => SelectionStart);
}
}
/// <summary>
/// Hold the selection length of the currently selected text.
/// </summary>
private int selectionLength = 0;
public int SelectionLength
{
get { return selectionLength; }
set
{
selectionLength = value;
UpdateStatusBar();
NotifyOfPropertyChange(() => SelectionLength);
}
}
/// <summary>
/// Gets or sets the TextLocation of the current editor control. If the
/// user is setting this value it will scroll the TextLocation into view.
/// </summary>
private TextLocation textLocation = new TextLocation(0, 0);
public TextLocation TextLocation
{
get { return textLocation; }
set
{
textLocation = value;
UpdateStatusBar();
NotifyOfPropertyChange(() => TextLocation);
}
}
And that's it! Done.
I hope this helps.
Edit. for all those looking for an example of working with AvalonEdit using MVVM, you can download a very basic editor application from http://1drv.ms/1E5nhCJ.
Notes. This application actually creates a MVVM friendly editor control by inheriting from the AvalonEdit standard control and adds additional Dependency Properties to it as appropriate - *this is different to what I have shown in the answer given above*. However, in the solution I have also shown how this can be done (as I describe in the answer above) using Attached Properties and there is code in the solution under the Behaviors namespace. What is actually implemented however, is the first of the above approaches.
Please also be aware that there is some code in the solution that is unused. This *sample* was a stripped back version of a larger application and I have left some code in as it could be useful to the user who downloads this example editor. In addition to the above, in the example code I access the Text by binding to document, there are some purest that may argue that this is not pure-MVVM, and I say "okay, but it works". Some times fighting this pattern is not the way to go.
I hope this of use to some of you.
Related
I'm playing with databinding on c# compact framework. I develop a simple form with a Textbox and a Label. I want to change the data binded to Textbox (bindModelTextBox) and show these changes by the Label (bindModelLabel), which is binded to the same data. Here is the code:
public partial class CreateShipment : Form {
//simple bean. Just one property: id, a string
private BasicShipmentBean toBindBasicShipment = null;
public CreateShipment() {
InitializeComponent();
BindingSource bsProva = new BindingSource();
toBindBasicShipment = new BasicShipmentBean();
toBindBasicShipment.id = "boo";
bsProva.Add(toBindBasicShipment);
bindModelLabel.DataBindings.Add("Text", bsProva, "id", true, DataSourceUpdateMode.OnPropertyChanged);
bindModelTextBox.DataBindings.Add("Text", bsProva, "id", true, DataSourceUpdateMode.OnPropertyChanged);
bindModelTextBox.LostFocus += textLoseFocus;
}
...
private void textLoseFocus(object sender, System.EventArgs e)
{
System.Diagnostics.Debug.WriteLine("focus lost. "+toBindBasicShipment.id);
}
When textbox loose focus I can see the data is updated in the bean, but, the label still shows bean's original id value. What am I missing?
You need to implement INotifyPropertyChanged on your BasicShipmentBean class. I forgot where exactly I found this originally, but here is an ObservableObject base class that implements INotifyPropertyChanged, that I use for all of my data sources.
public abstract class ObservableObject : INotifyPropertyChanged
{
#region Debugging Aides
/// <summary>
/// Warns the developer if this object does not have
/// a public property with the specified name. This
/// method does not exist in a Release build.
/// </summary>
[Conditional("DEBUG")]
[DebuggerStepThrough]
public virtual void VerifyPropertyName(string propertyName)
{
// Verify that the property name matches a real,
// public, instance property on this object.
if (TypeDescriptor.GetProperties(this)[propertyName] == null)
{
string msg = "Invalid property name: " + propertyName;
if (this.ThrowOnInvalidPropertyName)
throw new Exception(msg);
else
Debug.Fail(msg);
}
}
/// <summary>
/// Returns whether an exception is thrown, or if a Debug.Fail() is used
/// when an invalid property name is passed to the VerifyPropertyName method.
/// The default value is false, but subclasses used by unit tests might
/// override this property's getter to return true.
/// </summary>
protected virtual bool ThrowOnInvalidPropertyName { get; private set; }
#endregion // Debugging Aides
#region INotifyPropertyChanged Members
/// <summary>
/// Raises the PropertyChange event for the property specified
/// </summary>
/// <param name="propertyName">Property name to update. Is case-sensitive.</param>
public virtual void RaisePropertyChanged(string propertyName)
{
this.VerifyPropertyName(propertyName);
OnPropertyChanged(propertyName);
}
/// <summary>
/// Raised when a property on this object has a new value.
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Raises this object's PropertyChanged event.
/// </summary>
/// <param name="propertyName">The property that has a new value.</param>
protected virtual void OnPropertyChanged(string propertyName)
{
this.VerifyPropertyName(propertyName);
PropertyChangedEventHandler handler = this.PropertyChanged;
if (handler != null)
{
var e = new PropertyChangedEventArgs(propertyName);
handler(this, e);
}
}
#endregion // INotifyPropertyChanged Members
}
Then, you need to raise the OnPropertyChanged event in your setter for the id in BasicShipmentBean, e.g.:
private string _id;
public string id
{
get { return _id; }
set
{
if (value != _id)
{
_id = value;
OnPropertyChanged("id");
}
}
}
Data binding in the Compact Framework is a bit more tedious than in WPF, but much of the implementation is pretty similar.
My combobox returns a set of values from s stored procedure as this
private void BindCombo()
{
DataCombo.FillCombo(ComboDS(2313001), cmbClass, 0);
DataCombo.FillCombo(DDCombo(5007), cmbGroup, 0);
}
I managed to give a rudimentary auto complete suggestion as IsTextSearchenabled but cannot get a auto suggestion box that i would like.
I have seen loads of examples of autocomplete/suggestive textboxes but none of them seem to suit me.
this code apparently suits me.
but how would i use the auto suggest here
using System;
using System.ComponentModel;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
namespace DotNetZen.AutoFilteredComboBox
{
public class AutoFilteredComboBox : ComboBox
{
private int silenceEvents = 0;
/// <summary>
/// Creates a new instance of <see cref="AutoFilteredComboBox" />.
/// </summary>
public AutoFilteredComboBox()
{
DependencyPropertyDescriptor textProperty = DependencyPropertyDescriptor.FromProperty(
ComboBox.TextProperty, typeof(AutoFilteredComboBox));
textProperty.AddValueChanged(this, this.OnTextChanged);
this.RegisterIsCaseSensitiveChangeNotification();
}
#region IsCaseSensitive Dependency Property
/// <summary>
/// The <see cref="DependencyProperty"/> object of the <see cref="IsCaseSensitive" /> dependency property.
/// </summary>
public static readonly DependencyProperty IsCaseSensitiveProperty =
DependencyProperty.Register("IsCaseSensitive", typeof(bool), typeof(AutoFilteredComboBox), new UIPropertyMetadata(false));
/// <summary>
/// Gets or sets the way the combo box treats the case sensitivity of typed text.
/// </summary>
/// <value>The way the combo box treats the case sensitivity of typed text.</value>
[System.ComponentModel.Description("The way the combo box treats the case sensitivity of typed text.")]
[System.ComponentModel.Category("AutoFiltered ComboBox")]
[System.ComponentModel.DefaultValue(true)]
public bool IsCaseSensitive
{
[System.Diagnostics.DebuggerStepThrough]
get
{
return (bool)this.GetValue(IsCaseSensitiveProperty);
}
[System.Diagnostics.DebuggerStepThrough]
set
{
this.SetValue(IsCaseSensitiveProperty, value);
}
}
protected virtual void OnIsCaseSensitiveChanged(object sender, EventArgs e)
{
if (this.IsCaseSensitive)
this.IsTextSearchEnabled = false;
this.RefreshFilter();
}
private void RegisterIsCaseSensitiveChangeNotification()
{
System.ComponentModel.DependencyPropertyDescriptor.FromProperty(IsCaseSensitiveProperty, typeof(AutoFilteredComboBox)).AddValueChanged(
this, this.OnIsCaseSensitiveChanged);
}
#endregion
#region DropDownOnFocus Dependency Property
/// <summary>
/// The <see cref="DependencyProperty"/> object of the <see cref="DropDownOnFocus" /> dependency property.
/// </summary>
public static readonly DependencyProperty DropDownOnFocusProperty =
DependencyProperty.Register("DropDownOnFocus", typeof(bool), typeof(AutoFilteredComboBox), new UIPropertyMetadata(true));
/// <summary>
/// Gets or sets the way the combo box behaves when it receives focus.
/// </summary>
/// <value>The way the combo box behaves when it receives focus.</value>
[System.ComponentModel.Description("The way the combo box behaves when it receives focus.")]
[System.ComponentModel.Category("AutoFiltered ComboBox")]
[System.ComponentModel.DefaultValue(true)]
public bool DropDownOnFocus
{
[System.Diagnostics.DebuggerStepThrough]
get
{
return (bool)this.GetValue(DropDownOnFocusProperty);
}
[System.Diagnostics.DebuggerStepThrough]
set
{
this.SetValue(DropDownOnFocusProperty, value);
}
}
#endregion
#region | Handle selection |
/// <summary>
/// Called when <see cref="ComboBox.ApplyTemplate()"/> is called.
/// </summary>
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
this.EditableTextBox.SelectionChanged += this.EditableTextBox_SelectionChanged;
}
/// <summary>
/// Gets the text box in charge of the editable portion of the combo box.
/// </summary>
protected TextBox EditableTextBox
{
get
{
return ((TextBox)base.GetTemplateChild("PART_EditableTextBox"));
}
}
private int start = 0, length = 0;
private void EditableTextBox_SelectionChanged(object sender, RoutedEventArgs e)
{
if (this.silenceEvents == 0)
{
this.start = ((TextBox)(e.OriginalSource)).SelectionStart;
this.length = ((TextBox)(e.OriginalSource)).SelectionLength;
this.RefreshFilter();
}
}
#endregion
#region | Handle focus |
/// <summary>
/// Invoked whenever an unhandled <see cref="UIElement.GotFocus" /> event
/// reaches this element in its route.
/// </summary>
/// <param name="e">The <see cref="RoutedEventArgs" /> that contains the event data.</param>
protected override void OnGotFocus(RoutedEventArgs e)
{
base.OnGotFocus(e);
if (this.ItemsSource != null && this.DropDownOnFocus)
{
this.IsDropDownOpen = true;
}
}
#endregion
#region | Handle filtering |
private void RefreshFilter()
{
if (this.ItemsSource != null)
{
ICollectionView view = CollectionViewSource.GetDefaultView(this.ItemsSource);
view.Refresh();
this.IsDropDownOpen = true;
}
}
private bool FilterPredicate(object value)
{
// We don't like nulls.
if (value == null)
return false;
// If there is no text, there's no reason to filter.
if (this.Text.Length == 0)
return true;
string prefix = this.Text;
// If the end of the text is selected, do not mind it.
if (this.length > 0 && this.start + this.length == this.Text.Length)
{
prefix = prefix.Substring(0, this.start);
}
return value.ToString()
.StartsWith(prefix, !this.IsCaseSensitive, CultureInfo.CurrentCulture);
}
#endregion
/// <summary>
/// Called when the source of an item in a selector changes.
/// </summary>
/// <param name="oldValue">Old value of the source.</param>
/// <param name="newValue">New value of the source.</param>
protected override void OnItemsSourceChanged(System.Collections.IEnumerable oldValue, System.Collections.IEnumerable newValue)
{
if (newValue != null)
{
ICollectionView view = CollectionViewSource.GetDefaultView(newValue);
view.Filter += this.FilterPredicate;
}
if (oldValue != null)
{
ICollectionView view = CollectionViewSource.GetDefaultView(oldValue);
view.Filter -= this.FilterPredicate;
}
base.OnItemsSourceChanged(oldValue, newValue);
}
private void OnTextChanged(object sender, EventArgs e)
{
if (!this.IsTextSearchEnabled && this.silenceEvents == 0)
{
this.RefreshFilter();
// Manually simulate the automatic selection that would have been
// available if the IsTextSearchEnabled dependency property was set.
if (this.Text.Length > 0)
{
foreach (object item in CollectionViewSource.GetDefaultView(this.ItemsSource))
{
int text = item.ToString().Length, prefix = this.Text.Length;
this.SelectedItem = item;
this.silenceEvents++;
this.EditableTextBox.Text = item.ToString();
this.EditableTextBox.Select(prefix, text - prefix);
this.silenceEvents--;
break;
}
}
}
}
}
}
Also found the AutoFilteredComboBox to be very simple to work with. Though I have made some changes:
Removed use of DependencyPropertyDescriptor to avoid memory leak of combobox-objects
Introduced FilterItem-event and FilterList-event to allow one to customize the filtering
Changed default filtering from starts-with-string to contains-string
Removed support of having IsTextSearchEnabled enabled
Shows dropdown as soon one changes the search string, so search result is displayed
Example of how it is used:
<Controls:AutoFilteredComboBox ItemsSource="{Binding ViewModel.AvailableItems}"
SelectedValue="{Binding ViewModel.SelectedItem, Mode=TwoWay}"
IsEditable="True" IsTextSearchEnabled="False"/>
Improved version of AutoFilteredComboBox:
public class AutoFilteredComboBox : ComboBox
{
bool _ignoreTextChanged;
string _currentText;
/// <summary>
/// Creates a new instance of <see cref="AutoFilteredComboBox" />.
/// </summary>
public AutoFilteredComboBox()
{
if (System.ComponentModel.DesignerProperties.GetIsInDesignMode(this)) return;
}
public event Func<object, string, bool> FilterItem;
public event Action<string> FilterList;
#region IsCaseSensitive Dependency Property
/// <summary>
/// The <see cref="DependencyProperty"/> object of the <see cref="IsCaseSensitive" /> dependency property.
/// </summary>
public static readonly DependencyProperty IsCaseSensitiveProperty =
DependencyProperty.Register("IsCaseSensitive", typeof(bool), typeof(AutoFilteredComboBox), new UIPropertyMetadata(false));
/// <summary>
/// Gets or sets the way the combo box treats the case sensitivity of typed text.
/// </summary>
/// <value>The way the combo box treats the case sensitivity of typed text.</value>
[Description("The way the combo box treats the case sensitivity of typed text.")]
[Category("AutoFiltered ComboBox")]
[DefaultValue(true)]
public bool IsCaseSensitive
{
[System.Diagnostics.DebuggerStepThrough]
get
{
return (bool)this.GetValue(IsCaseSensitiveProperty);
}
[System.Diagnostics.DebuggerStepThrough]
set
{
this.SetValue(IsCaseSensitiveProperty, value);
}
}
#endregion
#region DropDownOnFocus Dependency Property
/// <summary>
/// The <see cref="DependencyProperty"/> object of the <see cref="DropDownOnFocus" /> dependency property.
/// </summary>
public static readonly DependencyProperty DropDownOnFocusProperty =
DependencyProperty.Register("DropDownOnFocus", typeof(bool), typeof(AutoFilteredComboBox), new UIPropertyMetadata(false));
/// <summary>
/// Gets or sets the way the combo box behaves when it receives focus.
/// </summary>
/// <value>The way the combo box behaves when it receives focus.</value>
[Description("The way the combo box behaves when it receives focus.")]
[Category("AutoFiltered ComboBox")]
[DefaultValue(false)]
public bool DropDownOnFocus
{
[System.Diagnostics.DebuggerStepThrough]
get
{
return (bool)this.GetValue(DropDownOnFocusProperty);
}
[System.Diagnostics.DebuggerStepThrough]
set
{
this.SetValue(DropDownOnFocusProperty, value);
}
}
#endregion
#region | Handle focus |
/// <summary>
/// Invoked whenever an unhandled <see cref="UIElement.GotFocus" /> event
/// reaches this element in its route.
/// </summary>
/// <param name="e">The <see cref="RoutedEventArgs" /> that contains the event data.</param>
protected override void OnGotFocus(RoutedEventArgs e)
{
base.OnGotFocus(e);
if (this.ItemsSource != null && this.DropDownOnFocus)
{
this.IsDropDownOpen = true;
}
}
#endregion
public override void OnApplyTemplate()
{
base.OnApplyTemplate();
AddHandler(TextBox.TextChangedEvent, new TextChangedEventHandler(OnTextChanged));
KeyUp += AutoFilteredComboBox_KeyUp;
this.IsTextSearchEnabled = false;
}
void AutoFilteredComboBox_KeyUp(object sender, KeyEventArgs e)
{
if (e.Key == Key.Down)
{
if (this.IsDropDownOpen == true)
{
// Ensure that focus is given to the dropdown list
if (Keyboard.FocusedElement is TextBox)
{
Keyboard.Focus(this);
if (this.Items.Count > 0)
{
if (this.SelectedIndex == -1 || this.SelectedIndex==0)
this.SelectedIndex = 0;
}
}
}
}
if (Keyboard.FocusedElement is TextBox)
{
if (e.OriginalSource is TextBox)
{
// Avoid the automatic selection of the first letter (As next letter will cause overwrite)
TextBox textBox = e.OriginalSource as TextBox;
if (textBox.Text.Length == 1 && textBox.SelectionLength == 1)
{
textBox.SelectionLength = 0;
textBox.SelectionStart = 1;
}
}
}
}
#region | Handle filtering |
private void RefreshFilter()
{
if (this.ItemsSource != null)
{
Action<string> filterList = FilterList;
if (filterList != null)
{
filterList(_currentText);
}
else
{
ICollectionView view = CollectionViewSource.GetDefaultView(this.ItemsSource);
view.Refresh();
}
this.SelectedIndex = -1; // Prepare so arrow down selects first
this.IsDropDownOpen = true;
}
}
private bool FilterPredicate(object value)
{
// We don't like nulls.
if (value == null)
return false;
// If there is no text, there's no reason to filter.
if (string.IsNullOrEmpty(_currentText))
return true;
Func<object, string, bool> filterItem = FilterItem;
if (filterItem != null)
return filterItem(value, _currentText);
if (IsCaseSensitive)
return value.ToString().Contains(_currentText);
else
return value.ToString().ToUpper().Contains(_currentText.ToUpper());
}
#endregion
protected override void OnSelectionChanged(SelectionChangedEventArgs e)
{
try
{
_ignoreTextChanged = true; // Ignore the following TextChanged
base.OnSelectionChanged(e);
}
finally
{
_ignoreTextChanged = false;
}
}
/// <summary>
/// Called when the source of an item in a selector changes.
/// </summary>
/// <param name="oldValue">Old value of the source.</param>
/// <param name="newValue">New value of the source.</param>
protected override void OnItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
{
if (newValue != null)
{
ICollectionView view = CollectionViewSource.GetDefaultView(newValue);
if (FilterList == null)
view.Filter += this.FilterPredicate;
}
if (oldValue != null)
{
ICollectionView view = CollectionViewSource.GetDefaultView(oldValue);
view.Filter -= this.FilterPredicate;
}
base.OnItemsSourceChanged(oldValue, newValue);
}
private void OnTextChanged(object sender, TextChangedEventArgs e)
{
if (_ignoreTextChanged)
return;
_currentText = Text;
if (!this.IsTextSearchEnabled)
{
this.RefreshFilter();
}
}
I have found a super simple workaround to my problem.
i created a preview text input event of the combobox.
then i just wrote
Combobox.IsDropDownOpen = true
may not the most elegant but works in my case
I currently have a requirement to notify my application user if any fields have been changed/updated on a View.
For example, if the user changes a date field on the View and then tries to close the View, the application would display a message asking the user to Continue and lose changes or Cancel so that they can click the Save button.
Problem is: How do I detect that any of the data fields changed in the View?
Hope this makes sense, than you in advance, regards,
One approach you can take is to leverage the IChangeTracking and INotifyPropertyChanged interfaces.
If you create an abstract base class that your view models inherit from (ViewModelBase) which implements the IChangeTracking and INotifyPropertyChanged interfaces, you can have your view model base attach to notification of property changes (in effect signaling that the view model has been modified) and which will set the IsChanged property to true to indicate that the view model is 'dirty'.
Using this approach, you are relying on property change notification via data binding to track changes and would reset the change tracking after any commits are made.
In the case you described you could handle the Unloaded or Closing event of your view to inspect the DataContext; and if the DataContext implements IChangeTracking you can use the IsChanged property to determine if any unaccepted changes have been made.
Simple example:
/// <summary>
/// Provides a base class for objects that support property change notification
/// and querying for changes and resetting of the changed status.
/// </summary>
public abstract class ViewModelBase : IChangeTracking, INotifyPropertyChanged
{
//========================================================
// Constructors
//========================================================
#region ViewModelBase()
/// <summary>
/// Initializes a new instance of the <see cref="ViewModelBase"/> class.
/// </summary>
protected ViewModelBase()
{
this.PropertyChanged += new PropertyChangedEventHandler(OnNotifiedOfPropertyChanged);
}
#endregion
//========================================================
// Private Methods
//========================================================
#region OnNotifiedOfPropertyChanged(object sender, PropertyChangedEventArgs e)
/// <summary>
/// Handles the <see cref="INotifyPropertyChanged.PropertyChanged"/> event for this object.
/// </summary>
/// <param name="sender">The source of the event.</param>
/// <param name="e">A <see cref="PropertyChangedEventArgs"/> that contains the event data.</param>
private void OnNotifiedOfPropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e != null && !String.Equals(e.PropertyName, "IsChanged", StringComparison.Ordinal))
{
this.IsChanged = true;
}
}
#endregion
//========================================================
// IChangeTracking Implementation
//========================================================
#region IsChanged
/// <summary>
/// Gets the object's changed status.
/// </summary>
/// <value>
/// <see langword="true"/> if the object’s content has changed since the last call to <see cref="AcceptChanges()"/>; otherwise, <see langword="false"/>.
/// The initial value is <see langword="false"/>.
/// </value>
public bool IsChanged
{
get
{
lock (_notifyingObjectIsChangedSyncRoot)
{
return _notifyingObjectIsChanged;
}
}
protected set
{
lock (_notifyingObjectIsChangedSyncRoot)
{
if (!Boolean.Equals(_notifyingObjectIsChanged, value))
{
_notifyingObjectIsChanged = value;
this.OnPropertyChanged("IsChanged");
}
}
}
}
private bool _notifyingObjectIsChanged;
private readonly object _notifyingObjectIsChangedSyncRoot = new Object();
#endregion
#region AcceptChanges()
/// <summary>
/// Resets the object’s state to unchanged by accepting the modifications.
/// </summary>
public void AcceptChanges()
{
this.IsChanged = false;
}
#endregion
//========================================================
// INotifyPropertyChanged Implementation
//========================================================
#region PropertyChanged
/// <summary>
/// Occurs when a property value changes.
/// </summary>
public event PropertyChangedEventHandler PropertyChanged;
#endregion
#region OnPropertyChanged(PropertyChangedEventArgs e)
/// <summary>
/// Raises the <see cref="INotifyPropertyChanged.PropertyChanged"/> event.
/// </summary>
/// <param name="e">A <see cref="PropertyChangedEventArgs"/> that provides data for the event.</param>
protected void OnPropertyChanged(PropertyChangedEventArgs e)
{
var handler = this.PropertyChanged;
if (handler != null)
{
handler(this, e);
}
}
#endregion
#region OnPropertyChanged(string propertyName)
/// <summary>
/// Raises the <see cref="INotifyPropertyChanged.PropertyChanged"/> event for the specified <paramref name="propertyName"/>.
/// </summary>
/// <param name="propertyName">The <see cref="MemberInfo.Name"/> of the property whose value has changed.</param>
protected void OnPropertyChanged(string propertyName)
{
this.OnPropertyChanged(new PropertyChangedEventArgs(propertyName));
}
#endregion
#region OnPropertyChanged(params string[] propertyNames)
/// <summary>
/// Raises the <see cref="INotifyPropertyChanged.PropertyChanged"/> event for the specified <paramref name="propertyNames"/>.
/// </summary>
/// <param name="propertyNames">An <see cref="Array"/> of <see cref="String"/> objects that contains the names of the properties whose values have changed.</param>
/// <exception cref="ArgumentNullException">The <paramref name="propertyNames"/> is a <see langword="null"/> reference (Nothing in Visual Basic).</exception>
protected void OnPropertyChanged(params string[] propertyNames)
{
if (propertyNames == null)
{
throw new ArgumentNullException("propertyNames");
}
foreach (var propertyName in propertyNames)
{
this.OnPropertyChanged(propertyName);
}
}
#endregion
}
In MVVM a View is binded to a View-Model which in turn is binded to a Model.
The view can not be dirty, since it's changes are reflected immediately to the View-Model.
If you want changes to be applied to Model only on "OK" or "Accept",
bind View to a View-Model that doesn't apply changes to Model,
until an ApplyCommand or AcceptCommand (that you define and implement) is executed.
(The commands that the View is binded to are implemented by the View-Model.)
Example - VM:
public class MyVM : INotifyPropertyChanged
{
public string MyText
{
get
{
return _MyText;
}
set
{
if (value == _MyText)
return;
_MyText = value;
NotifyPropertyChanged("MyText");
}
}
private string _MyText;
public string MyTextTemp
{
get
{
return _MyTextTemp;
}
set
{
if (value == _MyTextTemp)
return;
_MyTextTemp = value;
NotifyPropertyChanged("MyTextTemp");
NotifyPropertyChanged("IsTextDirty");
}
}
private string _MyTextTemp;
public bool IsTextDirty
{
get
{
return MyText != MyTextTemp;
}
}
public bool IsMyTextBeingEdited
{
get
{
return _IsMyTextBeingEdited;
}
set
{
if (value == _IsMyTextBeingEdited)
return;
_IsMyTextBeingEdited = value;
if (!value)
{
MyText = MyTextTemp;
}
NotifyPropertyChanged("IsMyTextBeingEdited");
}
}
private bool _IsMyTextBeingEdited;
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Example - View:
<Label Content="{Binding MyText}" />
<!-- You can translate the events to commands by using a suitable framework -->
<!-- or use code behind to update a new dependency property as in this example -->
<TextBox
LostFocus="TextBox_LostFocus"
GotFocus="TextBox_GotFocus"
Text="{Binding Path=MyTextTemp, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
/>
Example - view - code behind:
public MainWindow()
{
InitializeComponent();
SetBinding(IsTextBoxFocusedProperty,
new Binding
{
Path = new PropertyPath("IsMyTextBeingEdited"),
Mode = BindingMode.OneWayToSource,
});
}
private void TextBox_LostFocus(object sender, RoutedEventArgs e)
{
IsTextBoxFocused = false;
}
private void TextBox_GotFocus(object sender, RoutedEventArgs e)
{
IsTextBoxFocused = true;
}
#region IsTextBoxFocused
/// <summary>
/// Gets or Sets IsTextBoxFocused
/// </summary>
public bool IsTextBoxFocused
{
get
{
return (bool)this.GetValue(IsTextBoxFocusedProperty);
}
set
{
this.SetValue(IsTextBoxFocusedProperty, value);
}
}
/// <summary>
/// The backing DependencyProperty behind IsTextBoxFocused
/// </summary>
public static readonly DependencyProperty IsTextBoxFocusedProperty = DependencyProperty.Register(
"IsTextBoxFocused", typeof(bool), typeof(MainWindow), new PropertyMetadata(default(bool)));
#endregion
Idea: check entitystate:
Problem is that this refers to the whole VIEW, so when a new participant (refreshes form) is selected before any editing, the value is also "Modified". After a save, if nothing else changes and we don’t switch participants, the value is "Unchanged"
I have a combobox which binds to a collection of Foo on my viewmodel (FooCollection). I also set the SelectedItem property of the combobox to a property on my viewmodel of type Foo called SelectedFoo
I then set FooCollection and SelectedFoo and fire the appropriate OnPropertyChanged events.
My combobox contains the list of Foo, but the item displayed in the combobox is always the first item in the list. However, if you drop down the combobox, the item that is then highlighted is the correct item (SelectedFoo). Therefore, it is selecting the correct item, but not displaying it.
<ComboBox Grid.Row="5" ItemsSource="{Binding Path=FooCollection}"
SelectedItem="{Binding SelectedFoo, Mode=TwoWay}"
Name="FooSelectionControl"/>
Does anyone know how to fix this?
Hmm, it works on my end. What kind of collection are you using?
<ComboBox
SelectedItem="{Binding SelectedFoo, Mode=TwoWay}"
ItemsSource="{Binding FooCollection}">
</ComboBox>
Code behind:
public MainWindow()
{
InitializeComponent();
DataContext = this;
FooCollection = new BindingList<Foo>();
var foo = new Foo("Alpha");
FooCollection.Add(foo);
foo = new Foo("Beta");
SelectedFoo = foo;
FooCollection.Add(foo);
foo = new Foo("Gamma");
FooCollection.Add(foo);
}
public Foo SelectedFoo
{
get { return (Foo)GetValue(SelectedFooProperty); }
set { SetValue(SelectedFooProperty, value); }
}
public static readonly DependencyProperty SelectedFooProperty =
DependencyProperty.Register("SelectedFoo", typeof(Foo), typeof(MainWindow), new UIPropertyMetadata(null));
public BindingList<Foo> FooCollection
{
get { return (BindingList<Foo>)GetValue(FooCollectionProperty); }
set { SetValue(FooCollectionProperty, value); }
}
public static readonly DependencyProperty FooCollectionProperty =
DependencyProperty.Register("FooCollection", typeof(BindingList<Foo>), typeof(MainWindow), new UIPropertyMetadata(new BindingList<Foo>()));
and class Foo,
public class Foo : INotifyPropertyChanged
{
public Foo(string name)
{
_name = name;
}
private string _name;
public string Name
{
get { return _name; }
set
{
if (_name == value) return;
_name = value;
OnPropertyChanged("Name");
}
}
public override string ToString()
{
return Name;
}
#region INotifyPropertyChanged event
///<summary>
///Occurs when a property value changes.
///</summary>
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Raises the <see cref="PropertyChanged"/> event for
/// a given property.
/// </summary>
/// <param name="propertyName">The name of the changed property.</param>
protected void OnPropertyChanged(string propertyName)
{
//validate the property name in debug builds
VerifyProperty(propertyName);
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
/// <summary>
/// Verifies whether the current class provides a property with a given
/// name. This method is only invoked in debug builds, and results in
/// a runtime exception if the <see cref="OnPropertyChanged"/> method
/// is being invoked with an invalid property name. This may happen if
/// a property's name was changed but not the parameter of the property's
/// invocation of <see cref="OnPropertyChanged"/>.
/// </summary>
/// <param name="propertyName">The name of the changed property.</param>
[Conditional("DEBUG")]
private void VerifyProperty(string propertyName)
{
Type type = GetType();
//look for a *public* property with the specified name
PropertyInfo pi = type.GetProperty(propertyName);
if (pi == null)
{
//there is no matching property - notify the developer
string msg = "OnPropertyChanged was invoked with invalid property name {0}: ";
msg += "{0} is not a public property of {1}.";
msg = String.Format(msg, propertyName, type.FullName);
Debug.Fail(msg);
}
}
#endregion
}
Maybe try SelectedValue instead of SelectedItem. Also, make sure that Foo.Equals() is implemented correctly.
how to make scroll rule always at end of the ListView automatic without focus in WPF?
The answers from #pduncan and #MattBurland both have some problems, primarily that they fail to unregister the behaviour properly.
This implementation stores the handler in another attached property so that you can toggle the behaviour on and off, perhaps through a binding.
Note that this applies to ListView. If you are using ListBox, change occurrences of ListView to ListBox.
public static class ListViewExtensions
{
public static readonly DependencyProperty AutoScrollToEndProperty = DependencyProperty.RegisterAttached("AutoScrollToEnd", typeof(bool), typeof(ListViewExtensions), new UIPropertyMetadata(OnAutoScrollToEndChanged));
private static readonly DependencyProperty AutoScrollToEndHandlerProperty = DependencyProperty.RegisterAttached("AutoScrollToEndHandler", typeof(NotifyCollectionChangedEventHandler), typeof(ListViewExtensions));
public static bool GetAutoScrollToEnd(DependencyObject obj) => (bool)obj.GetValue(AutoScrollToEndProperty);
public static void SetAutoScrollToEnd(DependencyObject obj, bool value) => obj.SetValue(AutoScrollToEndProperty, value);
private static void OnAutoScrollToEndChanged(DependencyObject s, DependencyPropertyChangedEventArgs e)
{
var listView = s as ListView;
if (listView == null)
return;
var source = (INotifyCollectionChanged)listView.Items.SourceCollection;
if ((bool)e.NewValue)
{
NotifyCollectionChangedEventHandler scrollToEndHandler = delegate
{
if (listView.Items.Count <= 0)
return;
listView.Items.MoveCurrentToLast();
listView.ScrollIntoView(listView.Items.CurrentItem);
};
source.CollectionChanged += scrollToEndHandler;
listView.SetValue(AutoScrollToEndHandlerProperty, scrollToEndHandler);
}
else
{
var handler = (NotifyCollectionChangedEventHandler)listView.GetValue(AutoScrollToEndHandlerProperty);
source.CollectionChanged -= handler;
}
}
}
Use it like this:
<ListView local:ListViewExtensions.AutoScrollToEnd="{Binding Path=AutoScroll}">
I also made it a a static class, as you don't need to instantiate it (nor does it need to derive from DependencyObject). The cast to INotifyCollectionChanged was changed so that errors surface as cast exceptions, not NREs.
you can use this , its working for me :
this.myListView.ScrollIntoView(myListView.Items[myListView.Items.Count-1]);
if you need more advanced detail you can refere to this post
Since #pduncan's answer doesn't include the actual code, here is the code from the link they posted with only a minor modification from me:
public class ListBoxExtenders : DependencyObject
{
public static readonly DependencyProperty AutoScrollToEndProperty = DependencyProperty.RegisterAttached("AutoScrollToEnd", typeof(bool), typeof(ListBoxExtenders), new UIPropertyMetadata(default(bool), OnAutoScrollToEndChanged));
/// <summary>
/// Returns the value of the AutoScrollToEndProperty
/// </summary>
/// <param name="obj">The dependency-object whichs value should be returned</param>
/// <returns>The value of the given property</returns>
public static bool GetAutoScrollToEnd(DependencyObject obj)
{
return (bool)obj.GetValue(AutoScrollToEndProperty);
}
/// <summary>
/// Sets the value of the AutoScrollToEndProperty
/// </summary>
/// <param name="obj">The dependency-object whichs value should be set</param>
/// <param name="value">The value which should be assigned to the AutoScrollToEndProperty</param>
public static void SetAutoScrollToEnd(DependencyObject obj, bool value)
{
obj.SetValue(AutoScrollToEndProperty, value);
}
/// <summary>
/// This method will be called when the AutoScrollToEnd
/// property was changed
/// </summary>
/// <param name="s">The sender (the ListBox)</param>
/// <param name="e">Some additional information</param>
public static void OnAutoScrollToEndChanged(DependencyObject s, DependencyPropertyChangedEventArgs e)
{
var listBox = s as ListBox;
if (listBox != null)
{
var listBoxItems = listBox.Items;
var data = listBoxItems.SourceCollection as INotifyCollectionChanged;
var scrollToEndHandler = new System.Collections.Specialized.NotifyCollectionChangedEventHandler(
(s1, e1) =>
{
if (listBox.Items.Count > 0)
{
listBoxItems.MoveCurrentToLast();
listBox.ScrollIntoView(listBoxItems.CurrentItem);
}
});
if ((bool)e.NewValue)
data.CollectionChanged += scrollToEndHandler;
else
data.CollectionChanged -= scrollToEndHandler;
}
}
}
I modified it to use MoveCurrentToLast instead of getting the last item with listBox.Items[listBox.Items.Count - 1];. The reason for this (aside from being a little cleaner anyway) is that there is an edge case where if you have duplicate items in a list, then getting listBox.Items.Count - 1 and then scrolling to that item might not scroll you to the end of the list (it could even scroll you in the opposite direction!). It would instead scroll you to the first instance of that item.
Use an Attached Property. This article will show you how:
http://michlg.wordpress.com/2010/01/17/listbox-automatically-scroll-to-bottom/
For me, these work if each record in the list box is different. If they are the same it just scrolls to the first one that matches.