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Problems with user controls and Tab order

I've created a project with multiple user controls to support transparency, gradient and themes for winforms.
I was looking for a way to create a replacement for textbox, since winforms textboxes are not using the regular OnPaint and OnPaintBackground that other winforms control use, and sure enough, I've found something I can work with right here on stackoverflow. Brian's comment gave me the solution - Wrapping a transparent RichTextBox inside my own control.
However, this posed a new problem that I can't figure out how to solve - The TabIndex property dosn't operate as expected.
With normal textboxes, when you have multiple textboxes and each one have a different tab index, the focus goes from one textbox to the other in the order specified by the tab index. In my case, it doesn't. Instead, it's unpredictable.
I've tried multiple forms with different layouts and controls on them, but I can't seem to find any predictable pattern of behavior that would suggest the problem.
Here is the relevant control's code (the parent, ZControl inherits UserControl if that matters):
/// <summary>
/// A stylable textbox.
/// <Remarks>
/// The solution for writing a stylable textbox was inspired by this SO post and Brian's comment:
/// https://stackoverflow.com/a/4360341/3094533
/// </Remarks>
/// </summary>
[DefaultEvent("TextChanged")]
public partial class ZTextBox : ZControl
{
#region ctor
public ZTextBox()
{
TextBox = new TransparentRichTextBox();
TextBox.BackColor = Color.Transparent;
TextBox.BorderStyle = BorderStyle.None;
TextBox.Multiline = false;
TextBox.TextChanged += TextBox_TextChanged;
TextBox.TabStop = true;
TextBox.AcceptsTab = false;
InitializeComponent();
AdjustTextBoxRectangle();
this.Controls.Add(TextBox);
this.RoundedCorners.PropertyChanged += RoundedCorners_PropertyChanged;
}
#endregion ctor
#region properties
private TransparentRichTextBox TextBox { get; }
public override string Text
{
get
{
return TextBox.Text;
}
set
{
TextBox.Text = value;
}
}
[DefaultValue(false)]
public bool Multiline
{
get
{
return this.TextBox.Multiline;
}
set
{
this.TextBox.Multiline = value;
}
}
public override Font Font
{
get
{
return base.Font;
}
set
{
if (base.Font != value)
{
base.Font = value;
if (TextBox != null)
{
TextBox.Font = value;
}
}
}
}
public new int TabIndex
{
get
{
return this.TextBox.TabIndex;
}
set
{
this.TextBox.TabIndex = value;
}
}
#region hidden properties
[
DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
Browsable(false),
EditorBrowsable(EditorBrowsableState.Never)
]
public override Color ForeColor
{
get
{
return TextBox.ForeColor;
}
set
{
TextBox.ForeColor = value;
}
}
[
DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
Browsable(false),
EditorBrowsable(EditorBrowsableState.Never)
]
public override ContentAlignment TextAlign
{
get
{
return base.TextAlign;
}
set
{
base.TextAlign = value;
}
}
[
DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden),
Browsable(false),
EditorBrowsable(EditorBrowsableState.Never)
]
public override Point TextLocationOffset
{
get
{
return base.TextLocationOffset;
}
set
{
base.TextLocationOffset = value;
}
}
#endregion hidden properties
#endregion properties
#region methods
protected override void OnGotFocus(EventArgs e)
{
base.OnGotFocus(e);
TextBox.Focus();
}
protected override void DrawText(Graphics graphics, string text, ContentAlignment textAlign, Point locationOffset, Size stringSize)
{
// Do nothing - The transparent rich textbox is responsible for drawing the text...
}
protected override void OnResize(EventArgs e)
{
base.OnResize(e);
AdjustTextBoxRectangle();
}
private void AdjustTextBoxRectangle()
{
var corners = this.RoundedCorners.Corners;
var leftAdjustment = ((corners & RoundedEdges.TopLeft) == RoundedEdges.TopLeft || (corners & RoundedEdges.BottomLeft) == RoundedEdges.BottomLeft) ? this.RoundedCorners.ArcSize / 2 : 0;
var rightAdjustment = ((corners & RoundedEdges.TopRight) == RoundedEdges.TopRight || (corners & RoundedEdges.BottomRight) == RoundedEdges.BottomRight) ? this.RoundedCorners.ArcSize / 2 : 0;
TextBox.Top = 0;
TextBox.Left = leftAdjustment;
TextBox.Width = this.Width - leftAdjustment - rightAdjustment;
TextBox.Height = this.Height;
}
#endregion methods
#region event handlers
private void RoundedCorners_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
AdjustTextBoxRectangle();
}
private void TextBox_TextChanged(object sender, EventArgs e)
{
OnTextChanged(e);
}
#endregion event handlers
#region private classes
private class TransparentRichTextBox : RichTextBox
{
public TransparentRichTextBox()
{
this.SetStyle(ControlStyles.SupportsTransparentBackColor, true);
this.SetStyle(ControlStyles.Opaque, true);
this.SetStyle(ControlStyles.OptimizedDoubleBuffer, false);
}
protected override CreateParams CreateParams
{
get
{
CreateParams parms = base.CreateParams;
parms.ExStyle |= 0x20; // Turn on WS_EX_TRANSPARENT
return parms;
}
}
}
#endregion private classes
}
And the designer code, if that's relevant:
partial class ZTextBox
{
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.IContainer components = null;
/// <summary>
/// Clean up any resources being used.
/// </summary>
/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
#region Component Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.SuspendLayout();
//
// ZTextBox
//
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.None;
this.Name = "ZTextBox";
this.RoundedCorners.ArcSize = 50;
this.RoundedCorners.Corners = Zohar.UserControls.RoundedEdges.None;
this.Size = new System.Drawing.Size(100, 20);
this.Style.DisabledStyle.BackColor = System.Drawing.Color.Empty;
this.Style.DisabledStyle.BackgroundImage = null;
this.Style.DisabledStyle.BorderColor = System.Drawing.Color.Empty;
this.Style.DisabledStyle.ForeColor = System.Drawing.Color.Empty;
this.Style.DisabledStyle.Gradient.Angle = 0F;
this.Style.DisabledStyle.Gradient.BackColor = System.Drawing.Color.Empty;
this.Style.DisabledStyle.Image = null;
this.Style.DisabledStyle.Name = null;
this.Style.EnabledStyle.BackColor = System.Drawing.Color.Empty;
this.Style.EnabledStyle.BackgroundImage = null;
this.Style.EnabledStyle.BorderColor = System.Drawing.Color.Empty;
this.Style.EnabledStyle.ForeColor = System.Drawing.Color.Empty;
this.Style.EnabledStyle.Gradient.Angle = 0F;
this.Style.EnabledStyle.Gradient.BackColor = System.Drawing.Color.Empty;
this.Style.EnabledStyle.Image = null;
this.Style.EnabledStyle.Name = null;
this.Style.HoverStyle.BackColor = System.Drawing.Color.Empty;
this.Style.HoverStyle.BackgroundImage = null;
this.Style.HoverStyle.BorderColor = System.Drawing.Color.Empty;
this.Style.HoverStyle.ForeColor = System.Drawing.Color.Empty;
this.Style.HoverStyle.Gradient.Angle = 0F;
this.Style.HoverStyle.Gradient.BackColor = System.Drawing.Color.Empty;
this.Style.HoverStyle.Image = null;
this.Style.HoverStyle.Name = null;
this.ResumeLayout(false);
}
#endregion
}

The issue is caused by the following code:
public new int TabIndex
{
get
{
return this.TextBox.TabIndex;
}
set
{
this.TextBox.TabIndex = value;
}
}
You should never do this for UserControl (actually for any control). The documentation for Control.TabIndex property states:
Gets or sets the tab order of the control within its container.
In other words, the control TabIndex property is not global for the form, but scoped to the control container (parent).
The effect is that the form designer code where your control resides will call the shadow TabOrder setter, but the tab navigation handling will simply call the base Control property, leading to undetermined behavior.
Also note that setting the TabIndex of the inner TextBox makes no any sense since it's the only control inside the container (your control). While what you really need is to set the TabIndex of your control inside its container.
With that being said, simply remove the above code and everything will work as expected.

that's probably because you have not added your textbox's in order or maybe you deleted some of them while adding them, anyway you can choose the order on the properties of the controls => TabIndex

Can I have a Checked state on a ToolStripSplitButton in WinForms?

Is there a way to have a Checked state on a ToolStripSplitButton? I want to have a ToolStripButton with a Checked property to determine if an overlay is shown in my application's window. My users want to have direct interaction to control the opacity of the overlay, and to do that I imagine having a split button where the secondary button opens a slider bar to control the opacity. (That of course isn't standard functionality, but I'm confident of being able to put that together).
However, the ToolStripSplitButton doesn't have a Checked property, so I can't do that directly. I tried to have a standard ToolStripButton with a separate ToolStripSplitButton next to it, with the DropDownButtonWidth = 11, and Margin = -5, 1, 0, 2, so that it looks like it belongs to the ToolStripButton. It looks fine, but to complete the illusion of them being a single button, I need to get them to both to draw with the same VisualStyles.PushButtonState - so they both go Hot when the mouse is over either of them.
First I tried using the MouseEnter and MouseLeave events on both buttons to try to change the background color of the other button, but that had no effect. Then I tried to use the Paint event of each button to try to render them with the ButtonRenderer.DrawButton with a PushButtonState = Hot, but that didn't seem to be working either and was becoming very messy. It seems like there must be a better way!
Is there a simple, or at least a practical solution to this?
Edit: The effect I am after is something like this:

I suggest you to create your own UserControl and to use it as a ToolStripItem.
toolStripMenuItem.DropDownItems.Add(new ToolStripControlHost(new OverlayControl()));
Here is a simple example of the OverlayControl, which is deduced from your description (I suggest you to create a real UserControl with the Designer).
public class OverlayControl : UserControl
{
private readonly CheckBox _checkBox = new CheckBox();
private readonly TrackBar _trackBar = new TrackBar();
public ToolStripExtended()
{
_checkBox.Text = "Overlay";
BackColor = SystemColors.Window;
_checkBox.AutoSize = true;
_trackBar.AutoSize = true;
var flowLayoutPanel = new FlowLayoutPanel {AutoSize = true, AutoSizeMode = AutoSizeMode.GrowAndShrink};
flowLayoutPanel.Controls.AddRange( new Control[] { _checkBox, _trackBar });
Controls.Add(flowLayoutPanel);
AutoSize = true;
AutoSizeMode = AutoSizeMode.GrowAndShrink;
PerformLayout();
}
}

The solution that I came up with was to create my own button by inheriting from ToolStripSplitButton, add my own Checked property, and then manually draw over it when it is checked:
/// <summary>
/// ToolStripSplitCheckButton adds a Check property to a ToolStripSplitButton.
/// </summary>
public partial class ToolStripSplitCheckButton : ToolStripSplitButton
{
//==============================================================================
// Inner class: ToolBarButonSplitCheckButtonEventArgs
//==============================================================================
/// <summary>
/// The event args for the check button click event. To be able to use the OnCheckedChanged
/// event, we must also record a dummy button as well as this one (hack).
/// </summary>
public class ToolBarButonSplitCheckButtonEventArgs : ToolBarButtonClickEventArgs
{
/// <summary>
/// Constructor.
/// </summary>
/// <param name="split_button">The sender split check button</param>
public ToolBarButonSplitCheckButtonEventArgs(ToolStripSplitCheckButton split_button)
: base(new ToolBarButton("Dummy Button")) // Hack - Dummy Button is not used
{
SplitCheckButton = split_button;
}
/// <summary>
/// The ToolStripSplitCheckButton to be sent as an argument.
/// </summary>
public ToolStripSplitCheckButton SplitCheckButton { get; set; }
}
//==========================================================================
// Construction
public ToolStripSplitCheckButton()
{
m_checked = false;
m_mouse_over = false;
}
//==========================================================================
// Properties
/// <summary>
/// Indicates whether the button should toggle its Checked state on click.
/// </summary>
[Category("Behavior"),
Description("Indicates whether the item should toggle its selected state when clicked."),
DefaultValue(true)]
public bool CheckOnClick { get; set; }
/// <summary>
/// Indictates the Checked state of the button.
/// </summary>
[Category("Behavior"),
Description("Indicates whether the ToolStripSplitCheckButton is pressed in or not pressed in."),
DefaultValue(false)]
public bool Checked { get { return m_checked; } set { m_checked = value; } }
//==========================================================================
// Methods
/// <summary>
/// Toggle the click state on button click.
/// </summary>
protected override void OnButtonClick(EventArgs e)
{
if (CheckOnClick) {
m_checked = !m_checked;
// Raise the OnCheckStateChanged event when the button is clicked
if (OnCheckChanged != null) {
ToolBarButonSplitCheckButtonEventArgs args = new ToolBarButonSplitCheckButtonEventArgs(this);
OnCheckChanged(this, args);
}
}
base.OnButtonClick(e);
}
/// <summary>
/// On mouse enter, record that we are over the button.
/// </summary>
protected override void OnMouseEnter(EventArgs e)
{
m_mouse_over = true;
base.OnMouseEnter(e);
this.Invalidate();
}
/// <summary>
/// On mouse leave, record that we are no longer over the button.
/// </summary>
protected override void OnMouseLeave(EventArgs e)
{
m_mouse_over = false;
base.OnMouseLeave(e);
this.Invalidate();
}
/// <summary>
/// Paint the check highlight when required.
/// </summary>
protected override void OnPaint(PaintEventArgs e)
{
base.OnPaint(e);
if (m_checked) {
// I can't get the check + mouse over to render properly, so just give the button a colour fill - Hack
if (m_mouse_over) {
using (Brush brush = new SolidBrush(Color.FromArgb(64, SystemColors.MenuHighlight))) {
e.Graphics.FillRectangle(brush, ButtonBounds);
}
}
ControlPaint.DrawBorder(
e.Graphics,
e.ClipRectangle, // To draw around the button + drop-down
//this.ButtonBounds, // To draw only around the button
SystemColors.MenuHighlight,
ButtonBorderStyle.Solid);
}
}
//==========================================================================
// Member Variables
// The delegate that acts as a signature for the function that is ultimately called
// when the OnCheckChanged event is triggered.
public delegate void SplitCheckButtonEventHandler(object source, EventArgs e);
public event SplitCheckButtonEventHandler OnCheckChanged;
private bool m_checked;
private bool m_mouse_over;
}
To use this, handle the OnCheckChanged event for this button.
This has a couple of clunky hacks, however. To be able to raise an OnCheckedChanged event for the check button, the event args have to include a reference to an unused dummy button in addition to the actual button. And even after experimenting with various renderers, I couldn't get the checked + mouse over render to be exactly the same as that for a normal check button, so I just draw a colour overlay, which is nearly right but not quite.

Two Way Binding to AvalonEdit Document Text using MVVM

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.

AutoSuggestion in a WPF combobox

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

Static function as eventhandler in xaml

I am using this code to simulate the tab functionality in my silverlight application.
I would really like to avoid writing the function a lot of times because it has to be used on quite a lot of textboxes throughout the application. I have created a static class
public static class TabInsert
{
private const string Tab = " ";
public static void textBox_KeyDown(object sender, KeyEventArgs e)
{
TextBox textBox = sender as TextBox;
if (e.Key == Key.Tab)
{
int selectionStart = textBox.SelectionStart;
textBox.Text = String.Format("{0}{1}{2}",
textBox.Text.Substring(0, textBox.SelectionStart),
Tab,
textBox.Text.Substring(textBox.SelectionStart + textBox.SelectionLength, (textBox.Text.Length) - (textBox.SelectionStart + textBox.SelectionLength))
);
e.Handled = true;
textBox.SelectionStart = selectionStart + Tab.Length;
}
}
}
so that I can access it from various places liek this textBox.KeyDown += TabInsert.textBox_KeyDown;
Is there a way I can do this in XAML?

You can create a Behavior (System.Windows.Interactivity namespace) to easily attach to textboxes that in the OnAttached() override subscribes to the event and does the handling as you do and unsubscribes in OnDetaching().
Something like:
public class TabInsertBehavior : Behavior<TextBox>
{
/// <summary>
/// Called after the behavior is attached to an AssociatedObject.
/// </summary>
/// <remarks>
/// Override this to hook up functionality to the AssociatedObject.
/// </remarks>
protected override void OnAttached()
{
base.OnAttached();
this.AssociatedObject.KeyDown += textBox_KeyDown;
}
private const string Tab = " ";
public static void textBox_KeyDown(object sender, KeyEventArgs e)
{
TextBox textBox = sender as TextBox;
if (e.Key == Key.Tab)
{
int selectionStart = textBox.SelectionStart;
textBox.Text = String.Format("{0}{1}{2}",
textBox.Text.Substring(0, textBox.SelectionStart),
Tab,
textBox.Text.Substring(textBox.SelectionStart + textBox.SelectionLength, (textBox.Text.Length) - (textBox.SelectionStart + textBox.SelectionLength))
);
e.Handled = true;
textBox.SelectionStart = selectionStart + Tab.Length;
}
}
/// <summary>
/// Called when the behavior is being detached from its AssociatedObject, but before it has actually occurred.
/// </summary>
/// <remarks>
/// Override this to unhook functionality from the AssociatedObject.
/// </remarks>
protected override void OnDetaching()
{
base.OnDetaching();
this.AssociatedObject.KeyDown -= textBox_KeyDown;
}
}

Unfortunately, there is no direct way to do this in XAML.The event handlers you write in the code behind must be instance methods and cannot be static methods. These methods must be defined by the partial class within the CLR namespace identified by x:Class. You cannot qualify the name of an event handler to instruct a XAML processor to look for an event handler for event wiring in a different class scope.