Develop Reference

Recursive search cant find tabitem content (only header) [WPF | C#]

I've been busy experimenting with UWP and WPF. After some getting used to, sometimes stupid, quirks, I decided to make one of my signature... "way overscoped" projects in WPF.
Anyway I'm making an application where I need to bind properties in a static class to UI elements (and when the properties change the UI elements need to change too). I know bindings exist but I've been trying for ages to get the UI to update when the property changes (with INotifyPropertyChanged and the PropertyChanged eventhandler). Eventually, i gave up and decided to make my own binding system(kinda anyway... I've got expansions planned, which is why i want it to be custom).
working of the code:
[Design Time]
Basically, what i have to do is make a property in the VNClient class, add a BindingAttribute(string bindingName) to it and set the Tag of the UI element i want to bind it to to the bindingName. I've got that setup.
[Runtime (only once at startup)]
Now the code will get all properties from the VNClient class with a BindingAttribute and add them to a dictionary as keys, then it will recursively look through the XAML hierarchy and any element with a tag that is also in the dictionary (meaning its bindable) will be added as a value to the dictionary.
[Runtime (every time a property changes)]
An event is fired telling the BindingManager which property changed. It will then get that property name from the dictionary (along with a dependency property but that's not implemented yet) to see which UI elements are bound to that property, then it will change the correct property to the correct value.
Here is the BindingManager:
internal class BindingManager
{
Dictionary<string, List<FrameworkElement>> staticReferenceBindings = new();
public BindingManager()
{
VNClient.PropertyChanged += VNClient_PropertyChanged;
MainWindow.ApplicationLoaded += MainWindow_ApplicationLoaded;
}
private void MainWindow_ApplicationLoaded(object? sender, EventArgs e)
{
foreach (PropertyInfo property in typeof(VNClient).GetProperties())
{
BindingAttribute attr;
if ((attr = (BindingAttribute)property.GetCustomAttribute(typeof(BindingAttribute), false)) != null)
{
staticReferenceBindings.Add(property.Name, null);
}
}
FindBindings(VNClient.MainWindowInstance);
}
private async void VNClient_PropertyChanged(object? sender, (string bindTag, DependencyProperty bindProperty, dynamic value) e)
{
foreach (KeyValuePair<string, List<FrameworkElement>> Binding in staticReferenceBindings)
{
if (Binding.Value == null) continue;
foreach (FrameworkElement element in Binding.Value)
{
DependencyProperty modifiedProperty = e.bindProperty;
//Property conversion for different elements... like background property => fill property
if (Binding is Shape && e.bindProperty == Control.BackgroundProperty) modifiedProperty = Shape.FillProperty;
else if (Binding is Window && e.bindProperty == TextBlock.TextProperty) modifiedProperty = Window.TitleProperty;
if (modifiedProperty != null) element.SetValue(modifiedProperty, e.value);
}
}
}
internal void FindBindings(DependencyObject parent)
{
int childCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childCount; i++)
{
DependencyObject dpObject = VisualTreeHelper.GetChild(parent, i);
FrameworkElement child = dpObject as FrameworkElement;
if (child != null)
{
string childTag = child.Tag?.ToString();
if (childTag != null && staticReferenceBindings.ContainsKey(childTag))
{
if (staticReferenceBindings[childTag] == null) staticReferenceBindings[childTag] = new List<FrameworkElement>();
staticReferenceBindings[childTag].Add(child);
}
}
FindBindings(dpObject);
}
}
}
Here is an example property:
internal static event EventHandler<(string bindTag, DependencyProperty bindProperty, dynamic value)> PropertyChanged;
private static string _gameName = "*Insert name here :)*";
[BindingAttribute(nameof(GameName))]
public static string GameName
{
get
{
return _gameName;
}
set
{
if (_gameName != value) _gameName = value;
OnPropertyChanged(nameof(GameName), TextBlock.TextProperty, value);
}
}
private static void OnPropertyChanged(string bindTag, DependencyProperty bindProperty, dynamic value) => PropertyChanged?.Invoke(Application.Current, (bindTag, bindProperty, value));
And here is that property bound to a TextBlock:
<TabItem Height="60" Width="250" BorderThickness="1" Background="Transparent" BorderBrush="Black" Foreground="White">
<TabItem.Header>
<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<Image HorizontalAlignment="Left" Source="/Res/info_96px.png" Margin="0,0,180,0"/>
<TextBlock Text="About" HorizontalAlignment="Center" VerticalAlignment="Center" TextAlignment="Center" TextTrimming="None" Foreground="#BFFFFFFF"/>
</Grid>
</TabItem.Header>
<StackPanel>
<Image Source="/Res/Logo.png" HorizontalAlignment="Center" VerticalAlignment="Top" Height="150" Width="150"/>
<TextBlock Text="Made with *Insert name here :)*" HorizontalAlignment="Center"/>
<WrapPanel HorizontalAlignment="Center">
<!-- EXAMPLE BINDING --><TextBlock Text="{x:Static local:VNClient.GameName}" Tag="GameName" Margin="0,30,5,0" HorizontalAlignment="Center"/>
<TextBlock Text="was made with *Insert name here :)* version:" Margin="0,30,0,0" HorizontalAlignment="Center"/>
<TextBlock Text="{x:Static local:VNClient.EngineVersion}" Tag="EngineVersion" Margin="5,30,0,0" HorizontalAlignment="Center"/>
</WrapPanel>
</StackPanel>
</TabItem>
(static binding is so i can see the binding in the VS editor)
Okay, so, everything works fine BUT when this XAML element is in a TabItem my recursive search can only find the
<TabItem.Header/>
content NOT the
<TabItem.Content/>
meaning the bindings won't update... which is kinda not good...
If anyone has any idea besides "Just use the normal bindings..." that would be amazing
Thanks in advance :)
(and sorry if this is hard to read i am dyslexic)
EDIT:
I got it working by explicitly specifying, if it's a TabItem start another recursive search through it's content before continuing with it's header (it's a bandaid solution for sure, but I have yet to find bugs or similar problems with other controls like tab items)
[search result before]
Not all bindings found
[search result after]
As far as I can tell, all bindings found
[Modified recursive method in BindingManager]
internal void FindBindings(DependencyObject parent)
{
int childCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childCount; i++)
{
DependencyObject dpObject = VisualTreeHelper.GetChild(parent, i);
FrameworkElement child = dpObject as FrameworkElement;
if (child != null)
{
string childTag = child.Tag?.ToString();
if (childTag != null && staticReferenceBindings.ContainsKey(childTag))
{
if (staticReferenceBindings[childTag] == null) staticReferenceBindings[childTag] = new List<FrameworkElement>();
staticReferenceBindings[childTag].Add(child);
}
}
//New condition here
if (child is TabItem && ((TabItem)child).Content != null)
{
DependencyObject tabContent = ((TabItem)child).Content as DependencyObject;
FindBindings(tabContent);
}
FindBindings(dpObject);
}
}
if anyone still as anything to add to this or a more universal solution pls don't hesitate to comment.

Binding Errors on collapsed Gui Elements

I have a lot of bindings in a grid which are collapsed or visible based on the selecteditem in a treeview tree. so based on the object, the correct view pops up and the other collapses.
But I get lots of binding errors of the gui elements in the collapsed views. that is so, because I have a "myselecteditem" in the view model that fits to the view which is opened, but not to the collapsed ones.
is my approach stupid? can i suppress bindings for gui elemnts in a collapsed grid?
Code (shorted for lazy readers):
XAML:
<Grid x:Name="G_G_Content" Grid.Column="1">
<Grid x:Name="G_G_Abrechnung_Control" Visibility="Collapsed">
[...]
</Grid>
<Grid x:Name="G_G_Mitglied_Aktion" Visibility="Collapsed">
[...]
</Grid>
<Grid x:Name="G_G_Mitglied_Aktion_Nachweis" Visibility="Visible">
[...]
</Grid>
</Grid>
<TreeView
x:Name="G_tv_explorer"
Grid.Row="1"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
ItemsSource="{Binding TreeViewItemSource, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
SelectedItemChanged="G_tv_explorer_SelectedItemChanged"
TreeViewItem.Expanded="TreeViewItem_Expanded" />
C#:
private void G_tv_explorer_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
//set active treeviewitem
if (G_tv_explorer.SelectedItem != null)
{
//set treeview && ViMo
ViMo.TreeViewSelectedItem = e.NewValue;
RedrawGui();
ViMo.MySelectedItem = ((TreeViewItem)e.NewValue).Tag;
}
}
public void RedrawGui()
{
//redraw gui, dependant on selectedtreeviewitem
if (ViMo.TreeViewSelectedItem != null)
{
if(ViMo.TreeViewSelectedItem is string)
MessageBox.Show("Dummy");
else
{
//this is a placeholder
if (((TreeViewItem)ViMo.TreeViewSelectedItem).Header.ToString() == "Verwaltung")
{
G_G_Mitglied_Aktion_Nachweis.Visibility = System.Windows.Visibility.Collapsed;
G_G_Abrechnung_Control.Visibility = System.Windows.Visibility.Visible;
}
else if (((TreeViewItem)ViMo.TreeViewSelectedItem).Tag is MVVM.Model.Jahresabschluss)
{
G_G_Mitglied_Aktion_Nachweis.Visibility = System.Windows.Visibility.Collapsed;
G_G_Abrechnung.Visibility = System.Windows.Visibility.Visible;
}
}
}
}
Where RedrawGUI only sets the Grids Visible / collapsed based on the Object Type of the SelectedItem

WPF - Elements inside DataTemplate property issue when no binding?

I have the following TabControl:
<TabControl ItemsSource="{Binding Tabs"}>
<TabControl.ContentTemplate>
<DataTemplate DataType="{x:Type vm:TabVM}">
<TextBox></TextBox>
<TextBox Text="{Binding SomeProperty}"></TextBox>
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
The unexpected behaviour is that first TextBox has Text property shared between all tabitems, while second TextBox effectively bind to ViewModel property.
My need is to make independent the first TextBox too, even without binding.
What can I do ?
** UPDATE **
After several tries I've decided to use the ikriv's TabContent.cs.
The only issue I've found with this is that calling the TabControl.Items.Refresh() (i.e. after removing a tabItem) cause the reset of the internal cache.
An unelegant but effective solution may be this:
public ContentManager(TabControl tabControl, Decorator border)
{
_tabControl = tabControl;
_border = border;
_tabControl.SelectionChanged += (sender, args) => { UpdateSelectedTab(); };
/* CUSTOM */
var view = CollectionViewSource.GetDefaultView(((TabControl)_tabControl).Items);
view.CollectionChanged += View_CollectionChanged;
}
/*
* This fix the internal cache content when calling items->Refresh() method
* */
private void View_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
if (e.OldItems != null)
{
/* Retrieve all tabitems cache and store to a temp list */
IList<ContentControl> cachedContents = new List<ContentControl>();
foreach (var item in _tabControl.Items)
{
var tabItem = _tabControl.ItemContainerGenerator.ContainerFromItem(item);
var cachedContent = TabContent.GetInternalCachedContent(tabItem);
cachedContents.Add(cachedContent);
}
/* rebuild the view */
_tabControl.Items.Refresh();
/* Retrieve all cached content and store to the tabitems */
int idx = 0;
foreach (var item in _tabControl.Items)
{
var tabItem = _tabControl.ItemContainerGenerator.ContainerFromItem(item);
TabContent.SetInternalCachedContent(tabItem, cachedContents[idx++]);
}
}
}

You should use data binding since the same ContentTemplate will be applied for all items in your ItemsSource. Only the binding will be refreshed when you switch tabs basically. The TextBox isn't re-created nor reset.
What can I do ?
You could work around this in the view by handling the SelectionChanged event of the TabControl and reset the TextBox control yourself:
private void tabs_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
TabControl tc = sender as TabControl;
ContentPresenter cp = tc.Template.FindName("PART_SelectedContentHost", tc) as ContentPresenter;
if(cp != null && VisualTreeHelper.GetChildrenCount(cp) > 0)
{
ContentPresenter cpp = VisualTreeHelper.GetChild(cp, 0) as ContentPresenter;
if(cpp != null)
{
TextBox textBox = cpp.FindName("txt") as TextBox;
if (textBox != null)
textBox.Text = string.Empty;
}
}
}
<TabControl x:Name="tabs" ItemsSource="{Binding Tabs}" SelectionChanged="tabs_SelectionChanged">
<TabControl.ContentTemplate>
<DataTemplate>
<ContentPresenter>
<ContentPresenter.Content>
<StackPanel>
<TextBox x:Name="txt"></TextBox>
</StackPanel>
</ContentPresenter.Content>
</ContentPresenter>
</DataTemplate>
</TabControl.ContentTemplate>
</TabControl>
If you want to persist the text in the TextBox when you switch tabs you could use the attached behaviour from the following article and set its IsCached property to true: https://www.codeproject.com/articles/460989/wpf-tabcontrol-turning-off-tab-virtualization
<TabControl ItemsSource="{Binding Items}" behaviors:TabContent.IsCached="True">
<!-- Make sure that you don't set the TabControl's ContentTemplate property but the custom one here-->
<behaviors:TabContent.Template>
<DataTemplate>
<StackPanel>
<TextBox />
</StackPanel>
</DataTemplate>
</behaviors:TabContent.Template>
</TabControl>
Yet another approach would be to modify the ControlTemplate of the TabControl to include a ListBox as suggested by 'gekka' in the following thread on the MSDN forums: https://social.msdn.microsoft.com/Forums/en-US/4b71a43a-26f5-4fef-8dc5-55409262298e/using-uielements-on-datatemplate?forum=wpf

Two-way-binding: editing passed value from XAML control in the model setter does not update control

This is for a Windows 10 Universal App.
XAML:
<RelativePanel Padding="4" Margin="4,12,0,0">
<TextBlock x:Name="Label" Text="Class Name" Margin="12,0,0,4"/>
<ListView x:Name="ClassTextBoxes"
ItemsSource="{Binding TextBoxList}"
SelectionMode="None" RelativePanel.Below="Label">
<ListView.ItemTemplate>
<DataTemplate >
<RelativePanel>
<TextBox x:Name="tbox"
PlaceholderText="{Binding PlaceHolder}"
Text="{Binding BoxText,
Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}"
Padding="4" Width="200" MaxLength="25"/>
<TextBlock x:Name="errorLabel"
RelativePanel.Below="tbox"
Text="{Binding Error, Mode=TwoWay}"
Padding="0,0,0,4"
FontSize="10"
Foreground="Red"/>
<Button Content="Delete" Margin="12,0,0,0" RelativePanel.RightOf="tbox"/>
</RelativePanel>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</RelativePanel>
Model:
public class TextBoxStrings : BaseModel
{
private string _placeholder;
public string PlaceHolder
{
get { return _placeholder; }
set
{
if (_placeholder != value)
{
_placeholder = value;
NotifyPropertyChanged();
}
}
}
private string _boxText;
public string BoxText
{
get { return _boxText; }
set
{
if (_boxText != value)
{
_boxText = CheckBoxText(value);
NotifyPropertyChanged();
}
}
}
public string CheckBoxText(string val)
{
var r = new Regex("[^a-zA-Z0-9]+");
return r.Replace(val, "");
}
}
ViewModel:
private TrulyObservableCollection<TextBoxStrings> _textBoxList;
public TrulyObservableCollection<TextBoxStrings> TextBoxList
{
get { return _textBoxList; }
set
{
if (_textBoxList != value)
{
_textBoxList = value;
RaisePropertyChanged();
}
}
}
and I add new TextBoxString objects to my TextBoxList collection from within my view-model.
I want to make it that users can't type in certain characters (or rather, they get deleted whenever they
are typed in.
This works...in the model. Setting breakpoints and looking at the values, everything in the Model is working: value goes into the setter and gets changed, _boxText holds the new value that is set from CheckBoxText();
But the problem is, in my View, the textbox doesn't reflect changes to the underlying text that I make in the model.
So if I type in "abc*()" into "tbox", the value in the model will be "abc". The value of the textbox, however, will still be "abc*()".
I have a feeling it has something to do with the fact that I'm editing items that are inside of a collection and I don't have anything implemented to handle changing items within a collection. I was under the impression that using INotifyPropertyChanged and ObservableCollection<T> would take care of that for me.
Does anyone have any suggestions?
Thank you!
Edit: So, now I'm trying to use TrulyObservableCollection because I thought this was the problem, but it hasn't helped. Here it is: https://gist.github.com/itajaja/7507120

But the problem is, in my View, the textbox doesn't reflect changes to the underlying text that I make in the model.
As you've seen, the TextBox do reflect changes to your model. When you type in "abc*()" in the TextBox, the value in the model will be changed to "abc". The problem here is that the binding system in UWP is "intelligent". For TwoWay bindings, changes to the target will automatically propagate to the source and in this scenario, binding system assumes that the PropertyChanged event will fire for corresponding property in source and it ignores these events. So even you have RaisePropertyChanged or NotifyPropertyChanged in you source, the TextBox still won't update.
In WPF, we can call BindingExpression.UpdateTarget Method to force the update. But this method is not available in UWP.
As a workaround, you should be able to use TextBox.TextChanged event to check the input like following:
private void tbox_TextChanged(object sender, TextChangedEventArgs e)
{
var tb = sender as TextBox;
if (tb != null)
{
var originalText = tb.Text;
var r = new Regex("[^a-zA-Z0-9]+");
if (originalText != r.Replace(originalText, ""))
{
var index = (tb.SelectionStart - 1) < 0 ? 0 : (tb.SelectionStart - 1);
tb.Text = r.Replace(originalText, "");
tb.SelectionStart = index;
}
}
}
However it may break your MVVM model, you can use data validation to avoid this and here is a blog: Let’s Code! Handling validation in your Windows Store app (WinRT-XAML) you can refer to. And for my personal opinion, data validation is a better direction for this scenario.

if (_boxText != value)
{
_boxText = CheckBoxText(value);
NotifyPropertyChanged();
}
Try changing this to:
var tmp = CheckBoxText(value);
if (_boxText != tmp)
{
_boxText = tmp;
NotifyPropertyChanged();
}
I hope, in your XAML, the binding to property BoxText is two-way, right?

You should edit BoxText and then send checked value to UI. Just send value to CheckBoxText and already edited should be assigned to _boxText. And then you should send BoxText to UI by calling RaisePropertyChanged("BoxTest"). Please, see the following code snippet:
private string _boxText;
public string BoxText
{
get { return _boxText; }
set
{
if (_boxText != value)
{
_boxText=CheckBoxText(value);
RaisePropertyChanged("BoxText");
}
}
}
There is no difference where you use INotifyPropertyChanged for one property of for properties placed in collection. The complete example with collections and ListView can be seen here

How do I know that a Silverlight control has been displayed?

I have a list box displaying the names of help topics which can be added to and the names of the topics changed. Originally it was just displaying strings, but to get the inline editing working I changed it to use a custom type consisting of a string and an InEdit property so the UI can determine whether to display the TextBlock or TextBox:
XAML:
<ListBox ItemsSource="{Binding HelpTopics, Mode=TwoWay}"
SelectedValuePath="Description"
SelectedValue="{Binding SelectedPageId, Mode=TwoWay}"
SelectionChanged="ListBox_SelectionChanged">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<TextBlock Text="{Binding Description, Mode=TwoWay}"
VerticalAlignment="Center"
MouseLeftButtonUp="TopicTextBlock_MouseLeftButtonUp"
Visibility="{Binding InEdit, Converter={StaticResource boolToVisibilityConverter}, ConverterParameter=contra}"/>
<TextBox Text="{Binding Description, Mode=TwoWay}"
Visibility="{Binding InEdit, Converter={StaticResource boolToVisibilityConverter}, ConverterParameter=pro}"
LostFocus="EditTopicTextBox_LostFocus"
HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
<Button Margin="5" Content="Add Topic" Command="{Binding AddTopicCommand}"/>
HelpTopics is an ObservableCollection<EditableHelpTopic>.
SelectedPageId is a string.
boolToVisibilityConverter is a converter that does what it says.
What works:
Adding a topic creates a new item and adds it to the list and put the item in to edit mode.
Double clicking on an existing item puts that item into edit mode sets the focus to the TextBox and selects all the text so it can be overwritten.
When the TextBox loses focus the edit is saved and the display returns to the TextBlock.
What doesn't work:
When a new topic is added the TextBox should have focus and the text selected so the user can enter a new name.
So my question is is there a point in the code or an event where I know that the TextBox has been created and is visible so I can set focus and select its contents. I've tried hooking into the SelectionChanged event but when that fires the TextBox hasn't yet been displayed. I also added an event to the OnAddTopicExecute method in the view model which I handled in the view, but again that fired before the TextBox was visible.
Below is the code that supports the above XAML. I've tried to cut it down, but there still seems to be a lot of it, so you can skip this if you're not interested ;)
Code behind:
private DateTime lastClickTime = DateTime.MinValue;
private Point lastClickPosition;
private void TopicTextBlock_MouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
UIElement element = sender as UIElement;
if ((DateTime.Now - this.lastClickTime).TotalMilliseconds > 300)
{
this.lastClickPosition = e.GetPosition(element);
this.lastClickTime = DateTime.Now;
}
else
{
Point position = e.GetPosition(element);
if (Math.Abs(this.lastClickPosition.X - position.X) < 4 && Math.Abs(this.lastClickPosition.Y - position.Y) < 4)
{
var textBlock = sender as TextBlock;
var editableHelpTopic = textBlock.DataContext as EditableHelpTopic;
editableHelpTopic.InEdit = true;
var parent = textBlock.Parent as Grid;
TextBox textBox = parent.Children.First(c => c.GetType() == typeof(TextBox)) as TextBox;
textBox.Focus();
textBox.SelectAll();
}
}
}
private void EditTopicTextBox_LostFocus(object sender, RoutedEventArgs e)
{
var textBox = sender as TextBox;
var editableHelpTopic = textBox.DataContext as EditableHelpTopic;
editableHelpTopic.InEdit = false;
if (!textBox.Text.Equals(editableHelpTopic.Description))
{
this.editViewModel.RenameTopic(textBox.Text);
}
}
View Model:
public EditViewModel()
{
...
this.AddTopicCommand = new DelegateCommand(this.OnAddTopicExecute, this.OnAddTopicCanExecute);
...
}
where DelegateCommand is an implemetation of ICommand.
private void OnAddTopicExecute(object parameter)
{
var newTopic = new EditableHelpTopic
{
Description = "NewTopic",
InEdit = true
};
this.HelpTopics.Add(newTopic);
this.SelectedPageId = newTopic.Description;
}
Definitions:
public class EditableHelpTopic : INotifyPropertyChanged
{
public bool InEdit { ... }
public string Description { ... }
}

It turned out to be simpler than I thought.
I just needed to add a Loaded event handler to the TextBox:
private void EditTopicTextBox_Loaded(object sender, RoutedEventArgs e)
{
var textBox = sender as TextBox;
var editableHelpTopic = textBox.DataContext as EditableHelpTopic;
if (editableHelpTopic.InEdit)
{
textBox.Focus();
textBox.SelectAll();
}
}