Update TextBlock with binding not working

Update TextBlock with binding not working - c#

I have a question about databinding!
I am writing code for a 'node editor' that has some (different) nodes in it.
I use a BaseViewModel class that derives from INotifyPropertyChanged.
There is a 'base' NodeViewModel (that derives from it) with an ObservableCollection and other Properties, like the Node's Name property. It's implementation looks like this:
(in public class NodeViewModel : BaseViewModel):
protected String mName = String.Empty;
public String Name {
get { return mName; }
set {
if (mName == value) {
return;
}
mName = value;
OnPropertyChanged("Name");
}
}
With an OnPropertyChanged handler that looks like this:
(in BaseViewModel)
protected virtual void OnPropertyChanged(string propertyName) {
if (PropertyChanged != null) {
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
Now I have one additional RoomViewModel that derives from NodeViewModel.
I use another different ViewModel that I call RoomCollectionViewModel to group some rooms.
Now when I add a room to my roomcollection (by drawing a connection between them) I test all connected rooms for the same name.
If an already connected room exists in the collection with the same room name (e.g. "new room") I want to change those two room's names to e.g. "new room #1" and "new room #2". No problem so far.
Every node control (created using DataTemplates with set DataContext set to the ViewModel) contains a TextBlock (a modified one) that displays the node's name.
This is where it gets problematic:
I use a modified Textblock because I want to be able to modify the node's name by double-clicking on it. And that works perfectly, only if I modify the RoomViewModel's name in Code, this (modified) TextBlock won't update.
The strange thing is this:
When two equally named rooms in a collection get renamed by my code and I then double-click on the editable TextBlock (which converts to a TextBox in that process), I already see the modified Text. So I assume my DataBinding and my code is correct, just not complete :)
So how is it possible to force an update of my EditableTextBlock, the Text (DependencyProperty) seems to be updated correctly...
I hope you understand what my problem is! Thank you for any help.
Update 1
This is the XAML code for my EditableTextBlock (it comes from here: http://www.codeproject.com/Articles/31592/Editable-TextBlock-in-WPF-for-In-place-Editing)
<UserControl x:Class="NetworkUI.EditableTextBlock"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:local="clr-namespace:NetworkUI"
mc:Ignorable="d"
d:DesignHeight="60" d:DesignWidth="240" x:Name="mainControl">
<UserControl.Resources>
<DataTemplate x:Key="EditModeTemplate">
<TextBox KeyDown="TextBox_KeyDown" Loaded="TextBox_Loaded" LostFocus="TextBox_LostFocus"
Text="{Binding ElementName=mainControl, Path=Text, UpdateSourceTrigger=PropertyChanged}"
Margin="0" BorderThickness="1" />
</DataTemplate>
<DataTemplate x:Key="DisplayModeTemplate">
<TextBlock Text="{Binding ElementName=mainControl, Path=FormattedText}" Margin="5,3,5,3" MouseDown="TextBlock_MouseDown" />
</DataTemplate>
<Style TargetType="{x:Type local:EditableTextBlock}">
<Style.Triggers>
<Trigger Property="IsInEditMode" Value="True">
<Setter Property="ContentTemplate" Value="{StaticResource EditModeTemplate}" />
</Trigger>
<Trigger Property="IsInEditMode" Value="False">
<Setter Property="ContentTemplate" Value="{StaticResource DisplayModeTemplate}" />
</Trigger>
</Style.Triggers>
</Style>
</UserControl.Resources>
And here is the code-behind file:
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
namespace NetworkUI {
/// <summary>
/// Interaction logic for EditableTextBlock.xaml
/// </summary>
public partial class EditableTextBlock : UserControl {
#region Dependency Properties, Events
public static readonly DependencyProperty TextProperty =
DependencyProperty.Register("Text", typeof(String), typeof(EditableTextBlock),
new FrameworkPropertyMetadata("", FrameworkPropertyMetadataOptions.BindsTwoWayByDefault));
public static readonly DependencyProperty IsEditableProperty =
DependencyProperty.Register("IsEditable", typeof(Boolean), typeof(EditableTextBlock), new PropertyMetadata(true));
public static readonly DependencyProperty IsInEditModeProperty =
DependencyProperty.Register("IsInEditMode", typeof(Boolean), typeof(EditableTextBlock), new PropertyMetadata(false));
public static readonly DependencyProperty TextFormatProperty =
DependencyProperty.Register("TextFormat", typeof(String), typeof(EditableTextBlock), new PropertyMetadata("{0}"));
#endregion ///Dependency Properties, Events
#region Variables and Properties
/// <summary>
/// We keep the old text when we go into editmode
/// in case the user aborts with the escape key
/// </summary>
private String oldText;
/// <summary>
/// Text content of this EditableTextBlock
/// </summary>
public String Text {
get { return (String)GetValue(TextProperty); }
set { SetValue(TextProperty, value); }
}
/// <summary>
/// Is this EditableTextBlock editable or not
/// </summary>
public Boolean IsEditable {
get { return (Boolean)GetValue(IsEditableProperty); }
set { SetValue(IsEditableProperty, value); }
}
/// <summary>
/// Is this EditableTextBlock currently in edit mode
/// </summary>
public Boolean IsInEditMode {
get {
if (IsEditable)
return (Boolean)GetValue(IsInEditModeProperty);
else
return false;
}
set {
if (IsEditable) {
if (value)
oldText = Text;
SetValue(IsInEditModeProperty, value);
}
}
}
/// <summary>
/// The text format for the TextBlock
/// </summary>
public String TextFormat {
get { return (String)GetValue(TextFormatProperty); }
set {
if (value == "")
value = "{0}";
SetValue(TextFormatProperty, value);
}
}
/// <summary>
/// The formatted text of this EditablTextBlock
/// </summary>
public String FormattedText {
get { return String.Format(TextFormat, Text); }
}
#endregion ///Variables and Properties
#region Constructor
/// <summary>
/// Default constructor for the editable text block
/// </summary>
public EditableTextBlock() {
InitializeComponent();
Focusable = true;
FocusVisualStyle = null;
}
#endregion ///Constructor
#region Methods, Functions and Eventhandler
/// <summary>
/// Invoked when we enter edit mode
/// </summary>
/// <param name="sender">Sender</param>
/// <param name="e">Event arguments</param>
void TextBox_Loaded(object sender, RoutedEventArgs e) {
TextBox txt = sender as TextBox;
/// Give the TextBox input focus
txt.Focus();
txt.SelectAll();
}
/// <summary>
/// Invoked when we exit edit mode
/// </summary>
/// <param name="sender">Sender</param>
/// <param name="e">Event arguments</param>
void TextBox_LostFocus(object sender, RoutedEventArgs e) {
IsInEditMode = false;
}
/// <summary>
/// Invoked when the user edits the annotation.
/// </summary>
/// <param name="sender">Sender</param>
/// <param name="e">Event arguments</param>
void TextBox_KeyDown(object sender, KeyEventArgs e) {
if (e.Key == Key.Enter) {
IsInEditMode = false;
e.Handled = true;
}
else if (e.Key == Key.Escape) {
IsInEditMode = false;
Text = oldText;
e.Handled = true;
}
}
/// <summary>
/// Invoked when the user double-clicks on the textblock
/// to edit the text
/// </summary>
/// <param name="sender">Sender (the Textblock)</param>
/// <param name="e">Event arguments</param>
private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e) {
if (e.ClickCount == 2)
IsInEditMode = true;
}
#endregion ///Methods, Functions and Eventhandler
}
Thank you for any help!
Update 2
I changed the following line of code:
<TextBlock Text="{Binding ElementName=mainControl, Path=FormattedText}" Margin="5,3,5,3" MouseDown="TextBlock_MouseDown" />
to:
<TextBlock Text="{Binding ElementName=mainControl, Path=Text}" Margin="5,3,5,3" MouseDown="TextBlock_MouseDown" />
and now it is working!
I didn't see the TextBlock using the FormattedText in the first place! Ugh, thank you very much, now everything updates perfectly!

As postes by Lee O. the problem was indeed the bound property from my EditableTextBlock control.
The TextBlock used the FormattedText property that was updated by my Binding. Now I use the Text property for both, the TextBlock and the TextBox controls.
I simply removed the FormattedText property as well as the TextFormatProperty (DependencyProperty) and TextFormat property from my EditableTextBlock because I didn't plan to use those.
Thank you again!

Related

ComboBox stops updating when clicked / opened

I have a view with 2 ComboBoxes. When an item is selected in the first one, a list is get for the second one. The properties that link the view and view model are as follow:
In the code behind of the view I link the view and view model
var viewModel = new MetrologyFileViewModel();
DataContext = viewModel;
WPF:
<ComboBox ItemsSource="{Binding MetrologyProperties}"
SelectedIndex="{Binding NewSelectedMetrologyPropertyIndex}"
Grid.Column="1"
Grid.ColumnSpan="2"
Style="{StaticResource ComboBoxStyle1}" />
<ComboBox ItemsSource="{Binding NewMetrologyData}"
SelectedIndex="{Binding NewSelectedMetrologyDataIndex}"
Grid.Row="1"
Grid.Column="1"
Grid.ColumnSpan="2"
Style="{StaticResource ComboBoxStyle1}" />
C#:
/// <summary>
/// The new metrology property of the metrology data.
/// </summary>
public int NewSelectedMetrologyPropertyIndex
{
get { return _newSelectedMetrologyPropertyIndex; }
set
{
_newSelectedMetrologyPropertyIndex = value;
_newMetrologyData = _newSelectedMetrologyPropertyIndex > 0 ? new ObservableCollection<MetrologyData> { new MetrologyData() }.AddRange(DbServiceMetrologyData.GetOnProperty(MetrologyProperties[_newSelectedMetrologyPropertyIndex])) : null;
NotifyPropertyChanged();
NotifyPropertyChanged(nameof(NewMetrologyData));
}
}
/// <summary>
/// The new available metrology data that can be chosen from.
/// </summary>
public ObservableCollection<MetrologyData> NewMetrologyData
{
get { return _newMetrologyData; }
set
{
_newMetrologyData = value;
NotifyPropertyChanged();
}
}
/// <summary>
/// The new metrology data of the metrology fie.
/// </summary>
public int NewSelectedMetrologyDataIndex
{
get { return _newSelectedMetrologyDataIndex; }
set
{
_newSelectedMetrologyDataIndex = value;
NotifyPropertyChanged();
}
}
The AddRange method:
/// <summary>
/// Add a range of items to a <see cref="ObservableCollection{T}"/>.
/// </summary>
/// <typeparam name="T">The type of the <see cref="ObservableCollection{T}"/></typeparam>
/// <param name="sourceCollection">The <see cref="ObservableCollection{T}"/> where the items have to be added to.</param>
/// <param name="newCollection"><see cref="ObservableCollection{T}"/> with the new items.</param>
public static ObservableCollection<T> AddRange<T>(this ObservableCollection<T> sourceCollection, ObservableCollection<T> newCollection)
{
if (newCollection != null)
foreach (var item in newCollection)
sourceCollection.Add(item);
return sourceCollection;
}
The first time I select a property in the 1st ComboBox, the 2nd one updates fine though the view (I think) isn't fully updated because the space where the list should be displayed is very small (see picture).
This keeps working as long as I don't click the 2nd ComboBox. From the moment I open (click on) the 2nd ComboBox, it stops updating when I select a property in the 1st one.
Update
I found out that when just calling DbServiceMetrologyData.GetOnProperty(MetrologyProperties[_newSelectedMetrologyPropertyIndex]) the problem is fixed, I don't know why though.

I found out that when just calling DbServiceMetrologyData.GetOnProperty(MetrologyProperties[_newSelectedMetrologyPropertyIndex]) the problem is fixed, I don't know why though.

Extending TextBox in WPF using MahApps keeping Style

I made a custom textbox class for validating the input of the user to only allow Hexadecimal values, and used this new textbox (HexTextBox) in the xaml. It works well, but the HexTextBox looses all the style from the Mahapps, including color scheme and TextBoxHelper. Do you know how to use this extended TexBox and keep the style?
HexTextBox:
public class HexTextBox : TextBox
{
public HexTextBox()
{
}
/// <summary>
/// Raise when a keyboard key is pressed.
/// </summary>
/// <param name="e">The event args.</param>
protected override void OnPreviewKeyDown(KeyEventArgs e)
{
if (e.Key == Key.Space)
{
e.Handled = true;
}
base.OnPreviewKeyDown(e);
}
/// <summary>
/// Raise when a text will be inputed in the text box object.
/// </summary>
/// <param name="e">The event args.</param>
protected override void OnTextInput(TextCompositionEventArgs e)
{
int hexNumber;
e.Handled = !int.TryParse(e.Text, NumberStyles.HexNumber, CultureInfo.CurrentCulture, out hexNumber);
base.OnTextInput(e);
}
}
Window.xaml
<UserControl
...
xmlns:CoreWPF="clr-namespace:CoreWPF;assembly=CoreWPF"
...>
<CoreWPF:HexTextBox
Text="{Binding DataXor1, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
Grid.Column="2" Grid.Row="0"
controls:TextBoxHelper.ClearTextButton="True"
Height="26"
TextWrapping="Wrap"
CharacterCasing="Upper"
VerticalAlignment="Center"/>
Thanks in advance!

Create default style for your custom control which will be based on TextBox style.
<Style TargetType="Controls:HexTextBox" BasedOn="{StaticResource {x:Type TextBox}}"/>

Bindings inside WPF user control

In order to get into the WPF world and getting used to bindings, I've made a user control used to define a search filter. Depending on the wanted filter, the user can either enter a text, pick a date or select an item in a combo box. Here's an example with three instances of the created search control, each being of different type:
The good news is, everything is working but I'm not sure if everything has been done as intended.
SearchUserControl.xaml:
<UserControl x:Class="Zefix.View.UserControls.SearchUserControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
d:DesignHeight="82"
d:DesignWidth="300"
Height="Auto"
x:Name="SearchUserControlRoot">
<Grid>
<StackPanel>
<Label Name="LabelHeaderText" Content="{Binding HeaderText, ElementName=SearchUserControlRoot}" />
<TextBox Name="TextBoxSearchText" Text="{Binding SearchValue, ElementName=SearchUserControlRoot}" Visibility="{Binding TextBoxVisiblity, ElementName=SearchUserControlRoot}" />
<DatePicker Name="DatePickerSearch" SelectedDate="{Binding SearchValue, ElementName=SearchUserControlRoot}" Visibility="{Binding DatePickerVisiblity, ElementName=SearchUserControlRoot}" />
<ComboBox Name="ComboBoxSearch" Text="{Binding SearchValue, ElementName=SearchUserControlRoot}" ItemsSource="{Binding AvailableValues, ElementName=SearchUserControlRoot}" Visibility="{Binding ComboBoxVisiblity, ElementName=SearchUserControlRoot}" IsEditable="True" />
</StackPanel>
</Grid>
</UserControl>
SearchUserControl.xaml.cs:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Windows;
using Zefix.DataAccess;
namespace Zefix.View.UserControls {
/// <summary>
/// Interaction logic for SearchUserControl.xaml
/// </summary>
public partial class SearchUserControl {
#region Public Dependency Properties
/// <summary>
/// The search value property
/// </summary>
public static readonly DependencyProperty SearchValueProperty =
DependencyProperty.Register("SearchValue", typeof (object), typeof (SearchUserControl));
/// <summary>
/// The available values property
/// </summary>
public static readonly DependencyProperty AvailableValuesProperty =
DependencyProperty.Register("AvailableValues", typeof (IEnumerable<object>), typeof (SearchUserControl));
/// <summary>
/// The search type property
/// </summary>
public static readonly DependencyProperty SearchTypeProperty =
DependencyProperty.Register("SearchType", typeof (SearchType), typeof (SearchUserControl));
/// <summary>
/// The header text property
/// </summary>
public static readonly DependencyProperty HeaderTextProperty =
DependencyProperty.Register("HeaderText", typeof (string), typeof (SearchUserControl));
#endregion
#region Private Dependency Properties
/// <summary>
/// The combo box visiblity property
/// </summary>
private static readonly DependencyProperty ComboBoxVisiblityProperty =
DependencyProperty.Register("ComboBoxVisiblity", typeof (Visibility), typeof (SearchUserControl));
/// <summary>
/// The text box visiblity property
/// </summary>
private static readonly DependencyProperty TextBoxVisiblityProperty =
DependencyProperty.Register("TextBoxVisiblity", typeof (Visibility), typeof (SearchUserControl));
/// <summary>
/// The date picker visiblity property
/// </summary>
private static readonly DependencyProperty DatePickerVisiblityProperty =
DependencyProperty.Register("DatePickerVisiblity", typeof (Visibility), typeof (SearchUserControl));
#endregion
#region Public Properties
/// <summary>
/// Gets or sets the type of the search.
/// </summary>
/// <value>
/// The type of the search.
/// </value>
public SearchType SearchType {
get { return (SearchType) GetValue(SearchTypeProperty); }
set { SetValue(SearchTypeProperty, value); }
}
/// <summary>
/// Gets or sets the header text.
/// </summary>
/// <value>
/// The header text.
/// </value>
public string HeaderText {
get { return (string) GetValue(HeaderTextProperty); }
set { SetValue(HeaderTextProperty, value); }
}
/// <summary>
/// Gets or sets the available values.
/// </summary>
/// <value>
/// The available values.
/// </value>
public IEnumerable<object> AvailableValues {
get { return (IEnumerable<object>) GetValue(AvailableValuesProperty); }
set { SetValue(AvailableValuesProperty, value); }
}
/// <summary>
/// Gets or sets the search value.
/// </summary>
/// <value>
/// The search value.
/// </value>
public object SearchValue {
get { return GetValue(SearchValueProperty); }
set { SetValue(SearchValueProperty, value); }
}
#endregion
#region Private Properties
/// <summary>
/// Gets or sets the combo box visiblity.
/// </summary>
/// <value>
/// The combo box visiblity.
/// </value>
private Visibility ComboBoxVisiblity {
get { return (Visibility) GetValue(ComboBoxVisiblityProperty); }
set { SetValue(ComboBoxVisiblityProperty, value); }
}
/// <summary>
/// Gets or sets the date picker visiblity.
/// </summary>
/// <value>
/// The date picker visiblity.
/// </value>
private Visibility DatePickerVisiblity {
get { return (Visibility) GetValue(DatePickerVisiblityProperty); }
set { SetValue(DatePickerVisiblityProperty, value); }
}
/// <summary>
/// Gets or sets the text box visiblity.
/// </summary>
/// <value>
/// The text box visiblity.
/// </value>
private Visibility TextBoxVisiblity {
get { return (Visibility) GetValue(TextBoxVisiblityProperty); }
set { SetValue(TextBoxVisiblityProperty, value); }
}
#endregion
#region Constructor
/// <summary>
/// Initializes a new instance of the <see cref="SearchUserControl" /> class.
/// </summary>
public SearchUserControl() {
InitializeComponent();
DependencyPropertyDescriptor pd = DependencyPropertyDescriptor.FromProperty(SearchTypeProperty, typeof (SearchUserControl));
pd.AddValueChanged(this, OnSearchTypePropertyChanged);
// Initialize default parameters
SearchType = SearchType.Unknown;
}
#endregion
#region Private Methods
/// <summary>
/// Called when the search type property has changed.
/// </summary>
/// <param name="sender">The sender.</param>
/// <param name="e">The <see cref="EventArgs"/> instance containing the event data.</param>
private void OnSearchTypePropertyChanged(object sender, EventArgs e) {
// Hide all editors
DatePickerVisiblity = Visibility.Collapsed;
ComboBoxVisiblity = Visibility.Collapsed;
TextBoxVisiblity = Visibility.Collapsed;
// Make the correct editor visible
switch (SearchType) {
case SearchType.Date:
DatePickerVisiblity = Visibility.Visible;
break;
case SearchType.TextSelection:
ComboBoxVisiblity = Visibility.Visible;
break;
case SearchType.Text:
TextBoxVisiblity = Visibility.Visible;
break;
}
}
#endregion
}
}
Instantiation of the search controls from the parent control:
<ribbon:Tab Label="Search">
<ribbon:Group Padding="0,5,0,5">
<customcontrols:SearchUserControl x:Name="SearchUserControlCompanyName" HeaderText="company name" Margin="5,0,0,0" SearchType="Text" VerticalAlignment="Center" VerticalContentAlignment="Center" />
<customcontrols:SearchUserControl x:Name="SearchUserControlCompanyNationality" HeaderText="company nationality (ISO3 code)" Margin="5,0,0,0" SearchType="TextSelection" AvailableValues="{Binding Path=CompaniesViewModel.ISO3Codes}" VerticalAlignment="Center" />
<customcontrols:SearchUserControl x:Name="SearchUserControlDateFounded" HeaderText="date founded" Margin="5,0,0,0" SearchType="Date" VerticalAlignment="Center" VerticalContentAlignment="Center" />
<ribbon:Button Context="StatusBarItem" Name="ButtonApplyFilter" Label="Search" ImageSourceSmall="/Resources/search_magnifying_glass_find.png" Margin="5,0,0,0" VerticalAlignment="Center" Click="OnButtonApplyFilterClicked" Command="{Binding Path=ApplyFilterCommand}" ScreenTipHeader="Apply the search filter" VerticalContentAlignment="Center" VariantSize="Large" />
</ribbon:Group>
</ribbon:Tab>
In the SearchControl I wanted to display the correct component (textbox, datepicker or combobox) according to the set SearchType. For this the, xxxVisibility dependency properties and properties have been created (they are being set when the SearchTypeProperty notifies a property changed event). As there is no reason to expose them as public (they are being used only inside the SearchControl), I've made them private; MSDN states that bound properties MUST be public though. The project compiles and runs without an issue, but errors are being shown for the bound xxxVisibility properties with the message 'Public member expected' (can't tell if it's visual studio or resharper telling me that).
Is my approach to create this user control correct in respect to the WPF concepts?
Should the xxxVisibility properties be public (event though I don't want to expose them)?

This is a very difficult question to 'answer', rather than just 'comment' on. In my personal opinion, your UserControl has been written well and as far as I can see doesn't break any rules. Although I don't see any problem with declaring a private DependencyProperty, it is unusual. In this situation, developers often chose to implement a public Read Only DependencyProperty with a private DependencyPropertyKey instead:
private static readonly DependencyPropertyKey ComboBoxVisiblityPropertyKey
= DependencyProperty.RegisterReadOnly("ComboBoxVisiblity", typeof(int),
typeof(SearchUserControl), new PropertyMetadata(Visibility.Collapsed));
public static readonly DependencyProperty ComboBoxVisiblityProperty
= ComboBoxVisiblityPropertyKey.DependencyProperty;
public int ComboBoxVisiblity
{
get { return (int)GetValue(ComboBoxVisiblityProperty); }
protected set { SetValue(ComboBoxVisiblityPropertyKey, value); }
}
Some developers may also think it unusual that you are creating properties of type Visibility rather than binding bool values with BoolToVisibilityConverters, but again... that is your prerogative. Overall, well done! :)

Tab Navigation on Virtualized Items Panel

How can you set the Tab Navigation on virtualized items? As example;
<ListBox x:Name="Items">
<ListBox.Template>
<ControlTemplate>
<ScrollViewer HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto">
<ItemsPresenter/>
</ScrollViewer>
</ControlTemplate>
</ListBox.Template>
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel VirtualizingStackPanel.VirtualizationMode="Recycling"/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Button />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
If I set TabNavigation=Once or Cycle on the Scrollviewer itself, or the Listbox parent etc, it only tabs through items available in the viewport since the others haven't been generated yet. Is there a trick someone might share for when tabbing through Item Objects it will allow Tab to proceed to the next not-yet-virtualized item while bringing it to view in the viewport and providing intuitive tabbing through the controls?

So basically what was came up (thanks to the extra eyes and help of another fine dev) with was to go ahead and render the other items but while remaining virtualized from onload with a custom behavior and at the same time exposing a dependency for continuous scrolling and bringing the current item into view in the viewport;
namespace The.Namespace
{
using System;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
/// <summary>
/// Scroll selected item into view.
/// </summary>
public class ListBoxFocusBehavior : FocusBehavior<ListBox>
{
public static readonly DependencyProperty IsContinuousProperty = DependencyProperty.Register("IsContinuous",
typeof(bool),
typeof(ListBoxFocusBehavior),
new PropertyMetadata(
false,
(d, e) => ((ListBoxFocusBehavior)d).IsContinuousScroll = (bool)e.NewValue));
/// <summary>
/// Gets or sets a value indicating whether this instance is continuous.
/// </summary>
/// <value>
/// <c>true</c> if this instance is continuous; otherwise, <c>false</c>.
/// </value>
public bool IsContinuous
{
get { return (bool)GetValue(IsContinuousProperty); }
set { SetValue(IsContinuousProperty, value); }
}
/// <summary>
/// Called after the behavior is attached to an AssociatedObject.
/// </summary>
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.SelectionChanged += SelectionChanged;
AssociatedObject.KeyDown += KeyDown;
}
/// <summary>
/// Keys down.
/// </summary>
/// <param name="sender">The sender.</param>
/// <param name="e">The <see cref="System.Windows.Input.KeyEventArgs"/> instance containing the event data.</param>
private void KeyDown(object sender, KeyEventArgs e)
{
e.Handled = false;
if (e.Key == Key.Tab && Keyboard.Modifiers == ModifierKeys.None)
{
//forward tab ...
var idx = AssociatedObject.Items.IndexOf(AssociatedObject.SelectedItem);
if (idx < AssociatedObject.Items.Count-1)
{
AssociatedObject.SelectedItem = AssociatedObject.Items[idx + 1];
e.Handled = true;
}
}
if (e.Key == Key.Tab && (Keyboard.Modifiers & ModifierKeys.Shift) == ModifierKeys.Shift)
{
//back tab.
var idx = AssociatedObject.Items.IndexOf(AssociatedObject.SelectedItem);
if (idx > 0)
{
AssociatedObject.SelectedItem = AssociatedObject.Items[idx - 1];
e.Handled = true;
}
}
}
/// <summary>
/// Called when the behavior is being detached from its AssociatedObject, but before it has actually occurred.
/// </summary>
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.SelectionChanged -= SelectionChanged;
AssociatedObject.KeyDown -= KeyDown;
}
/// <summary>
/// Gots the focus.
/// </summary>
/// <param name="sender">The sender.</param>
/// <param name="e">The <see cref="System.Windows.RoutedEventArgs"/> instance containing the event data.</param>
private void GotFocus(object sender, RoutedEventArgs e)
{
if (AssociatedObject.SelectedItem == null && AssociatedObject.Items.Any())
{
AssociatedObject.SelectedItem = AssociatedObject.Items.First();
}
}
/// <summary>
/// Selections the changed.
/// </summary>
/// <param name="sender">The sender.</param>
/// <param name="e">The <see cref="System.Windows.Controls.SelectionChangedEventArgs"/> instance containing the event data.</param>
private void SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (AssociatedObject.SelectedItem == null) return;
AssociatedObject.UpdateLayout();
//have to, otherwise the listbox will probably not focus.
Action setFocus = () =>
{
AssociatedObject.UpdateLayout();
AssociatedObject.ScrollIntoView(AssociatedObject.SelectedItem);
//ensure that if the container did not exist yet (virtualized), it gets created.
AssociatedObject.UpdateLayout();
var container =
AssociatedObject.ItemContainerGenerator.ContainerFromItem(
AssociatedObject.SelectedItem) as Control;
if (container != null)
{
container.Focus();
}
};
AssociatedObject.Dispatcher.BeginInvoke(setFocus);
}
}
}

WPF MVVM Modal Overlay Dialog only over a View (not Window)

I'm pretty much new to the MVVM architecture design...
I was struggling lately to find a suitable control already written for such a purpose but had no luck, so I reused parts of XAML from another similar control and got make my own.
What I want to achieve is:
Have a reusable View (usercontrol) + viewmodel (to bind to) to be able to use inside other views as a modal overlay showing a dialog that disables the rest of the view, and shows a dialog over the it.
How I wanted to implement it:
create a viewmodel that takes string(message) and action+string collection(buttons)
viewmodel creates a collection of ICommands that call those actions
dialog view binds to the its viewmodel that will be exposed as property of another viewmodel (parent)
dialog view is put into the xaml of the parent like this:
pseudoXAML:
<usercontrol /customerview/ ...>
<grid>
<grid x:Name="content">
<various form content />
</grid>
<ctrl:Dialog DataContext="{Binding DialogModel}" Message="{Binding Message}" Commands="{Binding Commands}" IsShown="{Binding IsShown}" BlockedUI="{Binding ElementName=content}" />
</grid>
</usercontrol>
So here the modal dialog gets the datacontext from the DialogModel property of the Customer viewmodel, and binds commands and message. It would be also bound to some other element (here 'content') that needs to be disabled when the dialog shows (binding to IsShown). When you click some button in the dialog the associated command is called that simply calls the associated action that was passed in the constructor of the viewmodel.
This way I would be able to call Show() and Hide() of the dialog on the dialog viewmodel from inside the Customer viewmodel and alter the dialog viewmodel as needed.
It would give me only one dialog at a time but that is fine.
I also think that the dialog viewmodel would remain unittestable, since the unittests would cover the calling of the commands that ought to be created after it being created with Actions in the constructor. There would be a few lines of codebehind for the dialog view, but very little and pretty dumb (setters getters, with almost no code).
What concerns me is:
Is this ok?
Are there any problems I could get into?
Does this break some MVVM principles?
Thanks a lot!
EDIT: I posted my complete solution so you can have a better look. Any architectural comments welcome. If you see some syntax that can be corrected the post is flagged as community wiki.

Well not exactly an answer to my question, but here is the result of doing this dialog, complete with code so you can use it if you wish - free as in free speech and beer:
XAML Usage in another view (here CustomerView):
<UserControl
x:Class="DemoApp.View.CustomerView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:controls="clr-namespace:DemoApp.View"
>
<Grid>
<Grid Margin="4" x:Name="ModalDialogParent">
<put all view content here/>
</Grid>
<controls:ModalDialog DataContext="{Binding Dialog}" OverlayOn="{Binding ElementName=ModalDialogParent, Mode=OneWay}" IsShown="{Binding Path=DialogShown}"/>
</Grid>
</UserControl>
Triggering from parent ViewModel (here CustomerViewModel):
public ModalDialogViewModel Dialog // dialog view binds to this
{
get
{
return _dialog;
}
set
{
_dialog = value;
base.OnPropertyChanged("Dialog");
}
}
public void AskSave()
{
Action OkCallback = () =>
{
if (Dialog != null) Dialog.Hide();
Save();
};
if (Email.Length < 10)
{
Dialog = new ModalDialogViewModel("This email seems a bit too short, are you sure you want to continue saving?",
ModalDialogViewModel.DialogButtons.Ok,
ModalDialogViewModel.CreateCommands(new Action[] { OkCallback }));
Dialog.Show();
return;
}
if (LastName.Length < 2)
{
Dialog = new ModalDialogViewModel("The Lastname seems short. Are you sure that you want to save this Customer?",
ModalDialogViewModel.CreateButtons(ModalDialogViewModel.DialogMode.TwoButton,
new string[] {"Of Course!", "NoWay!"},
OkCallback,
() => Dialog.Hide()));
Dialog.Show();
return;
}
Save(); // if we got here we can save directly
}
Here is the code:
ModalDialogView XAML:
<UserControl x:Class="DemoApp.View.ModalDialog"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
x:Name="root">
<UserControl.Resources>
<ResourceDictionary Source="../MainWindowResources.xaml" />
</UserControl.Resources>
<Grid>
<Border Background="#90000000" Visibility="{Binding Visibility}">
<Border BorderBrush="Black" BorderThickness="1" Background="AliceBlue"
CornerRadius="10,0,10,0" VerticalAlignment="Center"
HorizontalAlignment="Center">
<Border.BitmapEffect>
<DropShadowBitmapEffect Color="Black" Opacity="0.5" Direction="270" ShadowDepth="0.7" />
</Border.BitmapEffect>
<Grid Margin="10">
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock Style="{StaticResource ModalDialogHeader}" Text="{Binding DialogHeader}" Grid.Row="0"/>
<TextBlock Text="{Binding DialogMessage}" Grid.Row="1" TextWrapping="Wrap" Margin="5" />
<StackPanel HorizontalAlignment="Stretch" VerticalAlignment="Bottom" Grid.Row="2">
<ContentControl HorizontalAlignment="Stretch"
DataContext="{Binding Commands}"
Content="{Binding}"
ContentTemplate="{StaticResource ButtonCommandsTemplate}"
/>
</StackPanel>
</Grid>
</Border>
</Border>
</Grid>
</UserControl>
ModalDialogView code behind:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
namespace DemoApp.View
{
/// <summary>
/// Interaction logic for ModalDialog.xaml
/// </summary>
public partial class ModalDialog : UserControl
{
public ModalDialog()
{
InitializeComponent();
Visibility = Visibility.Hidden;
}
private bool _parentWasEnabled = true;
public bool IsShown
{
get { return (bool)GetValue(IsShownProperty); }
set { SetValue(IsShownProperty, value); }
}
// Using a DependencyProperty as the backing store for IsShown. This enables animation, styling, binding, etc...
public static readonly DependencyProperty IsShownProperty =
DependencyProperty.Register("IsShown", typeof(bool), typeof(ModalDialog), new UIPropertyMetadata(false, IsShownChangedCallback));
public static void IsShownChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if ((bool)e.NewValue == true)
{
ModalDialog dlg = (ModalDialog)d;
dlg.Show();
}
else
{
ModalDialog dlg = (ModalDialog)d;
dlg.Hide();
}
}
#region OverlayOn
public UIElement OverlayOn
{
get { return (UIElement)GetValue(OverlayOnProperty); }
set { SetValue(OverlayOnProperty, value); }
}
// Using a DependencyProperty as the backing store for Parent. This enables animation, styling, binding, etc...
public static readonly DependencyProperty OverlayOnProperty =
DependencyProperty.Register("OverlayOn", typeof(UIElement), typeof(ModalDialog), new UIPropertyMetadata(null));
#endregion
public void Show()
{
// Force recalculate binding since Show can be called before binding are calculated
BindingExpression expressionOverlayParent = this.GetBindingExpression(OverlayOnProperty);
if (expressionOverlayParent != null)
{
expressionOverlayParent.UpdateTarget();
}
if (OverlayOn == null)
{
throw new InvalidOperationException("Required properties are not bound to the model.");
}
Visibility = System.Windows.Visibility.Visible;
_parentWasEnabled = OverlayOn.IsEnabled;
OverlayOn.IsEnabled = false;
}
private void Hide()
{
Visibility = Visibility.Hidden;
OverlayOn.IsEnabled = _parentWasEnabled;
}
}
}
ModalDialogViewModel:
using System;
using System.Windows.Input;
using System.Collections.ObjectModel;
using System.Collections.Generic;
using System.Windows;
using System.Linq;
namespace DemoApp.ViewModel
{
/// <summary>
/// Represents an actionable item displayed by a View (DialogView).
/// </summary>
public class ModalDialogViewModel : ViewModelBase
{
#region Nested types
/// <summary>
/// Nested enum symbolizing the types of default buttons used in the dialog -> you can localize those with Localize(DialogMode, string[])
/// </summary>
public enum DialogMode
{
/// <summary>
/// Single button in the View (default: OK)
/// </summary>
OneButton = 1,
/// <summary>
/// Two buttons in the View (default: YesNo)
/// </summary>
TwoButton,
/// <summary>
/// Three buttons in the View (default: AbortRetryIgnore)
/// </summary>
TreeButton,
/// <summary>
/// Four buttons in the View (no default translations, use Translate)
/// </summary>
FourButton,
/// <summary>
/// Five buttons in the View (no default translations, use Translate)
/// </summary>
FiveButton
}
/// <summary>
/// Provides some default button combinations
/// </summary>
public enum DialogButtons
{
/// <summary>
/// As System.Window.Forms.MessageBoxButtons Enumeration Ok
/// </summary>
Ok,
/// <summary>
/// As System.Window.Forms.MessageBoxButtons Enumeration OkCancel
/// </summary>
OkCancel,
/// <summary>
/// As System.Window.Forms.MessageBoxButtons Enumeration YesNo
/// </summary>
YesNo,
/// <summary>
/// As System.Window.Forms.MessageBoxButtons Enumeration YesNoCancel
/// </summary>
YesNoCancel,
/// <summary>
/// As System.Window.Forms.MessageBoxButtons Enumeration AbortRetryIgnore
/// </summary>
AbortRetryIgnore,
/// <summary>
/// As System.Window.Forms.MessageBoxButtons Enumeration RetryCancel
/// </summary>
RetryCancel
}
#endregion
#region Members
private static Dictionary<DialogMode, string[]> _translations = null;
private bool _dialogShown;
private ReadOnlyCollection<CommandViewModel> _commands;
private string _dialogMessage;
private string _dialogHeader;
#endregion
#region Class static methods and constructor
/// <summary>
/// Creates a dictionary symbolizing buttons for given dialog mode and buttons names with actions to berform on each
/// </summary>
/// <param name="mode">Mode that tells how many buttons are in the dialog</param>
/// <param name="names">Names of buttons in sequential order</param>
/// <param name="callbacks">Callbacks for given buttons</param>
/// <returns></returns>
public static Dictionary<string, Action> CreateButtons(DialogMode mode, string[] names, params Action[] callbacks)
{
int modeNumButtons = (int)mode;
if (names.Length != modeNumButtons)
throw new ArgumentException("The selected mode needs a different number of button names", "names");
if (callbacks.Length != modeNumButtons)
throw new ArgumentException("The selected mode needs a different number of callbacks", "callbacks");
Dictionary<string, Action> buttons = new Dictionary<string, Action>();
for (int i = 0; i < names.Length; i++)
{
buttons.Add(names[i], callbacks[i]);
}
return buttons;
}
/// <summary>
/// Static contructor for all DialogViewModels, runs once
/// </summary>
static ModalDialogViewModel()
{
InitTranslations();
}
/// <summary>
/// Fills the default translations for all modes that we support (use only from static constructor (not thread safe per se))
/// </summary>
private static void InitTranslations()
{
_translations = new Dictionary<DialogMode, string[]>();
foreach (DialogMode mode in Enum.GetValues(typeof(DialogMode)))
{
_translations.Add(mode, GetDefaultTranslations(mode));
}
}
/// <summary>
/// Creates Commands for given enumeration of Actions
/// </summary>
/// <param name="actions">Actions to create commands from</param>
/// <returns>Array of commands for given actions</returns>
public static ICommand[] CreateCommands(IEnumerable<Action> actions)
{
List<ICommand> commands = new List<ICommand>();
Action[] actionArray = actions.ToArray();
foreach (var action in actionArray)
{
//RelayExecuteWrapper rxw = new RelayExecuteWrapper(action);
Action act = action;
commands.Add(new RelayCommand(x => act()));
}
return commands.ToArray();
}
/// <summary>
/// Creates string for some predefined buttons (English)
/// </summary>
/// <param name="buttons">DialogButtons enumeration value</param>
/// <returns>String array for desired buttons</returns>
public static string[] GetButtonDefaultStrings(DialogButtons buttons)
{
switch (buttons)
{
case DialogButtons.Ok:
return new string[] { "Ok" };
case DialogButtons.OkCancel:
return new string[] { "Ok", "Cancel" };
case DialogButtons.YesNo:
return new string[] { "Yes", "No" };
case DialogButtons.YesNoCancel:
return new string[] { "Yes", "No", "Cancel" };
case DialogButtons.RetryCancel:
return new string[] { "Retry", "Cancel" };
case DialogButtons.AbortRetryIgnore:
return new string[] { "Abort", "Retry", "Ignore" };
default:
throw new InvalidOperationException("There are no default string translations for this button configuration.");
}
}
private static string[] GetDefaultTranslations(DialogMode mode)
{
string[] translated = null;
switch (mode)
{
case DialogMode.OneButton:
translated = GetButtonDefaultStrings(DialogButtons.Ok);
break;
case DialogMode.TwoButton:
translated = GetButtonDefaultStrings(DialogButtons.YesNo);
break;
case DialogMode.TreeButton:
translated = GetButtonDefaultStrings(DialogButtons.YesNoCancel);
break;
default:
translated = null; // you should use Translate() for this combination (ie. there is no default for four or more buttons)
break;
}
return translated;
}
/// <summary>
/// Translates all the Dialogs with specified mode
/// </summary>
/// <param name="mode">Dialog mode/type</param>
/// <param name="translations">Array of translations matching the buttons in the mode</param>
public static void Translate(DialogMode mode, string[] translations)
{
lock (_translations)
{
if (translations.Length != (int)mode)
throw new ArgumentException("Wrong number of translations for selected mode");
if (_translations.ContainsKey(mode))
{
_translations.Remove(mode);
}
_translations.Add(mode, translations);
}
}
#endregion
#region Constructors and initialization
public ModalDialogViewModel(string message, DialogMode mode, params ICommand[] commands)
{
Init(message, Application.Current.MainWindow.GetType().Assembly.GetName().Name, _translations[mode], commands);
}
public ModalDialogViewModel(string message, DialogMode mode, params Action[] callbacks)
{
Init(message, Application.Current.MainWindow.GetType().Assembly.GetName().Name, _translations[mode], CreateCommands(callbacks));
}
public ModalDialogViewModel(string message, Dictionary<string, Action> buttons)
{
Init(message, Application.Current.MainWindow.GetType().Assembly.GetName().Name, buttons.Keys.ToArray(), CreateCommands(buttons.Values.ToArray()));
}
public ModalDialogViewModel(string message, string header, Dictionary<string, Action> buttons)
{
if (buttons == null)
throw new ArgumentNullException("buttons");
ICommand[] commands = CreateCommands(buttons.Values.ToArray<Action>());
Init(message, header, buttons.Keys.ToArray<string>(), commands);
}
public ModalDialogViewModel(string message, DialogButtons buttons, params ICommand[] commands)
{
Init(message, Application.Current.MainWindow.GetType().Assembly.GetName().Name, ModalDialogViewModel.GetButtonDefaultStrings(buttons), commands);
}
public ModalDialogViewModel(string message, string header, DialogButtons buttons, params ICommand[] commands)
{
Init(message, header, ModalDialogViewModel.GetButtonDefaultStrings(buttons), commands);
}
public ModalDialogViewModel(string message, string header, string[] buttons, params ICommand[] commands)
{
Init(message, header, buttons, commands);
}
private void Init(string message, string header, string[] buttons, ICommand[] commands)
{
if (message == null)
throw new ArgumentNullException("message");
if (buttons.Length != commands.Length)
throw new ArgumentException("Same number of buttons and commands expected");
base.DisplayName = "ModalDialog";
this.DialogMessage = message;
this.DialogHeader = header;
List<CommandViewModel> commandModels = new List<CommandViewModel>();
// create commands viewmodel for buttons in the view
for (int i = 0; i < buttons.Length; i++)
{
commandModels.Add(new CommandViewModel(buttons[i], commands[i]));
}
this.Commands = new ReadOnlyCollection<CommandViewModel>(commandModels);
}
#endregion
#region Properties
/// <summary>
/// Checks if the dialog is visible, use Show() Hide() methods to set this
/// </summary>
public bool DialogShown
{
get
{
return _dialogShown;
}
private set
{
_dialogShown = value;
base.OnPropertyChanged("DialogShown");
}
}
/// <summary>
/// The message shown in the dialog
/// </summary>
public string DialogMessage
{
get
{
return _dialogMessage;
}
private set
{
_dialogMessage = value;
base.OnPropertyChanged("DialogMessage");
}
}
/// <summary>
/// The header (title) of the dialog
/// </summary>
public string DialogHeader
{
get
{
return _dialogHeader;
}
private set
{
_dialogHeader = value;
base.OnPropertyChanged("DialogHeader");
}
}
/// <summary>
/// Commands this dialog calls (the models that it binds to)
/// </summary>
public ReadOnlyCollection<CommandViewModel> Commands
{
get
{
return _commands;
}
private set
{
_commands = value;
base.OnPropertyChanged("Commands");
}
}
#endregion
#region Methods
public void Show()
{
this.DialogShown = true;
}
public void Hide()
{
this._dialogMessage = String.Empty;
this.DialogShown = false;
}
#endregion
}
}
ViewModelBase has :
public virtual string DisplayName { get; protected set; }
and implements INotifyPropertyChanged
Some resources to put in the resource dictionary:
<!--
This style gives look to the dialog head (used in the modal dialog)
-->
<Style x:Key="ModalDialogHeader" TargetType="{x:Type TextBlock}">
<Setter Property="Background" Value="{StaticResource Brush_HeaderBackground}" />
<Setter Property="Foreground" Value="White" />
<Setter Property="Padding" Value="4" />
<Setter Property="HorizontalAlignment" Value="Stretch" />
<Setter Property="Margin" Value="5" />
<Setter Property="TextWrapping" Value="NoWrap" />
</Style>
<!--
This template explains how to render the list of commands as buttons (used in the modal dialog)
-->
<DataTemplate x:Key="ButtonCommandsTemplate">
<ItemsControl IsTabStop="False" ItemsSource="{Binding}" Margin="6,2">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Button MinWidth="75" Command="{Binding Path=Command}" Margin="4" HorizontalAlignment="Right">
<TextBlock Text="{Binding Path=DisplayName}" Margin="2"></TextBlock>
</Button>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" HorizontalAlignment="Center" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
</ItemsControl>
</DataTemplate>

I have a custom open source FrameworkElement on my GitHub page that allows you to display modal content over the primary content.
The control can be used like this:
<c:ModalContentPresenter IsModal="{Binding DialogIsVisible}">
<TabControl Margin="5">
<Button Margin="55"
Padding="10"
Command="{Binding ShowModalContentCommand}">
This is the primary Content
</Button>
</TabItem>
</TabControl>
<c:ModalContentPresenter.ModalContent>
<Button Margin="75"
Padding="50"
Command="{Binding HideModalContentCommand}">
This is the modal content
</Button>
</c:ModalContentPresenter.ModalContent>
</c:ModalContentPresenter>
Features:
Displays arbitrary content.
Does not disable the primary content whilst the modal content is being displayed.
Disables mouse and keyboard access to the primary content whilst the modal content is displayed.
Is only modal to the content it is covering, not the entire application.
can be used in an MVVM friendly way by binding to the IsModal property.

I would approach this as a service that gets injected into your ViewModel, along the lines of the sample code below. To the extent what you want to do is in fact message box behavior, I would have my service implementation use a MessageBox!
I am using KISS here in order to present the concept. No code behind, and completely unit testable as shown.
As an aside, that Josh Smith example you are working off of was incredibly helpful to me also, even if it doesn't cover everything
HTH,
Berry
/// <summary>
/// Simple interface for visually confirming a question to the user
/// </summary>
public interface IConfirmer
{
bool Confirm(string message, string caption);
}
public class WPFMessageBoxConfirmer : IConfirmer
{
#region Implementation of IConfirmer
public bool Confirm(string message, string caption) {
return MessageBox.Show(message, caption, MessageBoxButton.YesNo) == MessageBoxResult.Yes;
}
#endregion
}
// SomeViewModel uses an IConfirmer
public class SomeViewModel
{
public ShellViewModel(ISomeRepository repository, IConfirmer confirmer)
{
if (confirmer == null) throw new ArgumentNullException("confirmer");
_confirmer = confirmer;
...
}
...
private void _delete()
{
var someVm = _masterVm.SelectedItem;
Check.RequireNotNull(someVm);
if (detailVm.Model.IsPersistent()) {
var msg = string.Format(GlobalCommandStrings.ConfirmDeletion, someVm.DisplayName);
if(_confirmer.Confirm(msg, GlobalCommandStrings.ConfirmDeletionCaption)) {
_doDelete(someVm);
}
}
else {
_doDelete(someVm);
}
}
...
}
// usage in the Production code
var vm = new SomeViewModel(new WPFMessageBoxConfirmer());
// usage in a unit test
[Test]
public void DeleteCommand_OnExecute_IfUserConfirmsDeletion_RemovesSelectedItemFrom_Workspaces() {
var confirmerMock = MockRepository.GenerateStub<IConfirmer>();
confirmerMock.Stub(x => x.Confirm(Arg<string>.Is.Anything, Arg<string>.Is.Anything)).Return(true);
var vm = new ShellViewModel(_repository, _crudConverter, _masterVm, confirmerMock, _validator);
vm.EditCommand.Execute(null);
Assert.That(vm.Workspaces, Has.Member(_masterVm.SelectedItem));
Assert.That(vm.Workspaces, Is.Not.Empty);
vm.DeleteCommand.Execute(null);
Assert.That(vm.Workspaces, Has.No.Member(_masterVm.SelectedItem));
Assert.That(vm.Workspaces, Is.Empty);
}

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