Develop Reference

Datatrigger appropriately changes the initial property of TextBlock but not after the object changes

Issue
When setting datatriggers for my textblock it accepts the default value without issue and changes the foreground appropriately however, when the the value changes it doesn't change colors as one would expect. I looked through a few answers and I should be able to reference the relative-source in someway but it didn't change the result.
XAML Test Code
<ListBox Name="test" Width="90" Margin="20,0,20,40" MouseDown="TextBlock_MouseDownTest"
ScrollViewer.VerticalScrollBarVisibility="Disabled">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Name="dttBlock" Text="{Binding Time}" MouseDown="TextBlock_MouseDownTest">
<TextBlock.Style>
<Style TargetType="TextBlock">
<Style.Triggers>
<DataTrigger Binding="{Binding Path =Flex}" Value="normal">
<Setter Property="Foreground" Value="Blue" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
MouseDownClickEvent
private void TextBlock_MouseDownTest(object sender, MouseButtonEventArgs e)
{
TimeLord item = (TimeLord) (sender as TextBlock).DataContext;
var textBlock = sender as TextBlock;
switch (item.Flex)
{
case "off":
MessageBox.Show("Normal ON");
item.Flex = "normal";
break;
case "normal":
MessageBox.Show("Flex ON");
item.Flex = "flex";
break;
case "flex":
MessageBox.Show("OFF");
item.Flex = "off";
break;
}
}
Prior Implementation and Desired Result
If the person responding doesn't mind, I would like to have a larger discussion on this. The reason I'm using data triggers is because I was having trouble implementing a button that resets all of my listboxitem foregrounds to the default color (Black).
Current XAML Code
<ListBox Name="friday" Width="90" Margin="20,0,20,40" MouseDown="TextBlock_MouseDown"
ScrollViewer.VerticalScrollBarVisibility="Disabled" IsSynchronizedWithCurrentItem="True">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Time}" MouseDown="TextBlock_MouseDown" />
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
Current C# ButtonClickEvent Code
private void clear_Click(object sender, RoutedEventArgs e)
{
List<System.Windows.Controls.ListBox> weekdays = new List<System.Windows.Controls.ListBox>
{monday, tuesday, wednesday, jueves, friday};
for (var i = 0; i < weekdays.Count; i++)
{
foreach (TimeLord item in weekdays[i].Items)
{
item.Flex = "off";
}
}
}
I have no problems changing the object associated with the listboxitem but I have no way of changing the foreground from the button itself. I can successfully change the foreground by creating an event for when the listboxitem is clicked by using the sender being passed into the event. If there is a way I can access the textbox from the ButtonClick event, that could be an alternative solution to the Datatrigger.
This is a small clip showing off the old implementation and that I can currently change the value of the item.

In my TimeLord class I never implemented the INotifyPropertyChanged, after doing so everything worked as I expected it to with the DataTriggers.
TimeLord.cs
public class TimeLord : INotifyPropertyChanged {
protected void OnPropertyChanged(PropertyChangedEventArgs e)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
handler(this, e);
}
public string flex;
public string Flex
{
get { return flex;}
set
{
flex = value;
OnPropertyChanged();
}
}
public string Time
{
get;
set;
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
public void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
XAML Code Block (It's the same one as before but just to show more than the one trigger type)
<DataTemplate>
<TextBlock Name="dttBlock" Text="{Binding Time}" MouseDown="TextBlock_MouseDownTest">
<TextBlock.Style>
<Style TargetType="TextBlock">
<Style.Triggers>
<DataTrigger Binding="{Binding Path =Flex}" Value="normal">
<Setter Property="Foreground" Value="Blue" />
</DataTrigger>
<DataTrigger Binding="{Binding Path =Flex}" Value="flex">
<Setter Property="Foreground" Value="Red" />
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</DataTemplate>

WPF: DataTrigger not firing

In a WPF Project I have some restyled DataGridColumnHeaders of a DataGrid which show a ComboBox for each DataGridColumnHeader. When the user selects from the ComboBox's the SelectionChanged handler (in the code behind) updates an Array of ColumnOptionViewModel objects on the MainWindowViewModel with the newest selection.
At this point some code also works out if there are any duplicate selections in this array, and then sets an IsDuplicate Boolean property on the ColumnOptionViewModel that are duplicates. The idea is that a DataTrigger picks up the change in IsDuplicate and changes the Background of a TextBlock in the DataTemplate of the ItemTemplate for the duplicate ComboBox's to Red.
However, this trigger is not firing. The IsDuplicate properties are being set ok, and everything else works as expected. What am I doing wrong?
Here is the XAML for the Window:
<Window x:Class="TestDataGrid.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:TestDataGrid"
mc:Ignorable="d"
Title="MainWindow" Height="350" Width="525">
<Grid>
<DataGrid Grid.Row="1" x:Name="dataGrid" ItemsSource="{Binding Records}">
<DataGrid.ColumnHeaderStyle>
<Style TargetType="DataGridColumnHeader">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<StackPanel>
<ComboBox x:Name="cbo"
ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type DataGrid}},Path=DataContext.ColumnOptions}"
SelectionChanged="cbo_SelectionChanged">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock x:Name="txt" Text="{Binding Name}"/>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding ElementName=cbo, Path=SelectedItem.IsDuplicate}">
<Setter TargetName="txt" Property="Background" Value="Red"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
</StackPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</DataGrid.ColumnHeaderStyle>
</DataGrid>
</Grid>
CODE BEHIND:
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
this.DataContext = new MainWindowViewModel(RecordProvider.GetRecords());
}
private void cbo_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
var vm = (MainWindowViewModel)DataContext;
var selectionChangedCombo = (ComboBox)e.Source;
var dataGridColumnHeader = selectionChangedCombo.TemplatedParent as DataGridColumnHeader;
vm.ColumnSelections[dataGridColumnHeader.DisplayIndex] = selectionChangedCombo.SelectedItem as ColumnOptionViewModel;
CheckForDuplicates();
}
private void CheckForDuplicates()
{
var vm = (MainWindowViewModel)DataContext;
var duplicates = vm.ColumnSelections.GroupBy(x => x.Name)
.Where(g => g.Skip(1).Any())
.SelectMany(g => g);
foreach (var option in duplicates)
{
option.IsDuplicate = true;
}
}
}
MainWindowViewModel :
public class MainWindowViewModel : ViewModelBase
{
public ObservableCollection<ColumnOptionViewModel> _columnOptions = new ObservableCollection<ColumnOptionViewModel>();
public ObservableCollection<RecordViewModel> _records = new ObservableCollection<RecordViewModel>();
ColumnOptionViewModel[] _columnSelections = new ColumnOptionViewModel[3];
public MainWindowViewModel(IEnumerable<Record> records)
{
foreach (var rec in records)
{
Records.Add(new RecordViewModel(rec));
}
ColumnOptions.Add(new ColumnOptionViewModel(TestDataGrid.ColumnOptions.ColumnOption1));
ColumnOptions.Add(new ColumnOptionViewModel(TestDataGrid.ColumnOptions.ColumnOption2));
ColumnOptions.Add(new ColumnOptionViewModel(TestDataGrid.ColumnOptions.ColumnOption3));
ColumnSelections[0] = ColumnOptions[0];
ColumnSelections[1] = ColumnOptions[1];
ColumnSelections[2] = ColumnOptions[2];
}
public ObservableCollection<ColumnOptionViewModel> ColumnOptions
{
get { return _columnOptions; }
set { _columnOptions = value; }
}
public ColumnOptionViewModel[] ColumnSelections
{
get { return _columnSelections; }
set { _columnSelections = value; }
}
public ObservableCollection<RecordViewModel> Records
{
get { return _records; }
set { _records = value; }
}
}
ColumnOptionViewModel :
public class ColumnOptionViewModel : ViewModelBase
{
ColumnOptions _colOption;
public ColumnOptionViewModel(ColumnOptions colOption )
{
_colOption = colOption;
}
public string Name
{
get { return _colOption.ToString(); }
}
public override string ToString()
{
return Name;
}
private bool _isDuplicate = false;
public bool IsDuplicate
{
get { return _isDuplicate; }
set
{ _isDuplicate = value;
OnPropertyChanged();
}
}
}
EDIT:
ViewModelBase :
public abstract class ViewModelBase : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}

If you are trying to bind to the IsDuplicate property of the SelectedItem in the ComboBox you could use a RelativeSource.
You should also set the Value property of the DataTrigger to true/false depending on when you want the Background property of the TextBlock to be set to Red:
<ComboBox x:Name="cbo" ItemsSource="{Binding RelativeSource={RelativeSource AncestorType={x:Type DataGrid}},Path=DataContext.ColumnOptions}"
SelectionChanged="cbo_SelectionChanged">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock x:Name="txt" Text="{Binding Name}"/>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Path=SelectedItem.IsDuplicate, RelativeSource={RelativeSource AncestorType=ComboBox}}" Value="True">
<Setter TargetName="txt" Property="Background" Value="Red"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>

As #mm8 said, the Value is not chosen in your DataTrigger.
If that doesn't work, you can try using Trigger directly on TextBlock instead of DataTemplate.Triggers:
<TextBlock>
<TextBlock.Style>
<Style TargetType="TextBlock">
<Setter Property="Background" Value="White"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Path=IsDuplicate}" Value="True">
<Setter Property="Background" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
Also, background and foreground values in controls that have selectable items can be tricky. For example, you may want to disable default selection colors (unfortunately then you will have to manage selected/focused background yourself):
<ComboBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent" />
</ComboBox.Resources>

WPF ListBox data validation

I have a ListBox of string items where I want to validate the strings every time a string is added or removed.
Below is the code I've cobbled together, but the problem is that ValidateAddresses is never called when the ObservableCollection Addresses changes.
Intended behavior is that when an invalid string is found, a red border should be shown around the ListBox with a tooltip that displays the error message.
This INotifyDataErrorInfo setup works fine for TextBoxes, so I dunno what I am doing wrong here.
ViewModel
[CustomValidation(typeof(ItemViewModel), "ValidateAddresses")]
public ObservableCollection<string> Addresses
{
get
{
return item.Addresses;
}
set
{
item.Addresses = value;
NotifyPropertyChanged(nameof(Addresses));
}
}
XAML
<Grid>
<Grid.Resources>
<Style TargetType="ListBox">
<Setter Property="Margin" Value="5"/>
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
<Setter Property="Validation.ErrorTemplate">
<Setter.Value>
<ControlTemplate x:Name="TextErrorTemplate">
<DockPanel LastChildFill="True">
<AdornedElementPlaceholder>
<Border BorderBrush="Red" BorderThickness="2"/>
</AdornedElementPlaceholder>
<TextBlock Foreground="Red"/>
</DockPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="True">
<Setter Property="ToolTip" Value="{Binding RelativeSource={x:Static RelativeSource.Self}, Path=(Validation.Errors).CurrentItem.ErrorContent}"/>
</Trigger>
</Style.Triggers>
</Style>
</Grid.Resources>
<ListBox ItemsSource="{Binding Path=Item.Addresses, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnNotifyDataErrors=True}" SelectedIndex="{Binding Path=SelectedAddress, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
</Grid>
Validation method (never called)
public static ValidationResult ValidateAddresses(object obj, ValidationContext context)
{
ItemViewModel item = (ItemViewModel)context.ObjectInstance;
if (item.Addresses.Count > 0)
{
foreach (string address in item.Addresses)
{
if (Regex.IsMatch(address, #"[^\w]"))
return new ValidationResult($"{address} is not a valid address.", new List<string> { "Addresses" });
}
}
return ValidationResult.Success;
}

I ended up adding following in class constructor for each ObservableCollection I had.
Addresses.CollectionChanged += (sender, eventArgs) => { NotifyPropertyChanged(nameof(Addresses)); };
I tried to look into circumstances upon which unsubscribing from events is required to prevent memory leaks, but it does not seem like this is one of these cases so cleanup shouldn't be required.
Null check is not required because ObservableCollections are all initialized in Model class constructor.
Thank you for your replies.
And this is the code for NotifyPropertyChanged.
public class ObservableObject : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void NotifyPropertyChanged([CallerMemberName] string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}

CanUserAddRows New Row not saving in DataGrid

Created DataGrid and set CanUserAddRows="True"
Have a button which saves updates in the cs file:
private void Save_Click(object sender, RoutedEventArgs e)
{
UnitService unitService = new UnitService();
unitService.SaveUpdates(valuationCase);
MainWindow mainWin = new MainWindow();
mainWin.Show();
this.Close();
}
There is also a textbox not in the datagrid on the window which is editable and this is correctly saving edits with the save click button. Just the new rows aren't.
Any ideas??
datagrid definition:
<DataGrid Name="dgCommentsList" AutoGenerateColumns="False" Margin="10,196,9.953,38.204" CanUserAddRows="True" FontSize="18">
<DataGrid.ColumnHeaderStyle>
<Style TargetType="DataGridColumnHeader">
<Setter Property="FontSize" Value="20" />
<Setter Property="FontWeight" Value="bold" />
</Style>
</DataGrid.ColumnHeaderStyle>
<DataGrid.Columns>
<DataGridTemplateColumn Header="Type" >
<DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<TextBox x:Name="Type" Text="{Binding Type}" >
<TextBox.Style>
<Style TargetType="TextBox">
<Style.Triggers>
<DataTrigger Binding="{Binding IsReadOnly}" Value="False">
<Setter Property="TextBox.IsReadOnly" Value="False"/>
</DataTrigger>
<DataTrigger Binding="{Binding IsReadOnly}" Value="True">
<Setter Property="TextBox.IsReadOnly" Value="True"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
</DataTemplate>
</DataGridTemplateColumn.CellTemplate>
</DataGridTemplateColumn>
</DataGrid>

I think you need to set the mode of the binding for it to write back to the underlying object.Plus I noticed your DataGrid does not have an ItemsSource. I'm guessing as this was just a snippet that you left it out.
<TextBox x:Name="Type" Text="{Binding Type, Mode=TwoWay}">

You should commit the edit on the row using dataGrid.CommitEdit()
Edit: After diagnosing the issue here goes
You either need to implement INotifyPropertyChanged on your DataContext class (i.e: Viewmodel) like so:
public class ViewModel: INotifyPropertyChanged
{
private string _type;
public string Type
{
get { return _type; }
set
{
_type = value;
OnPropertyChanged("Type");
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName = null)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
Or you extend from DependencyObject and use Dependency Properties, like so:
public class ViewModel: DependencyObject
{
public static readonly DependencyProperty TypeProperty = DependencyProperty.Register(
"Type", typeof (string), typeof (ViewModel), new PropertyMetadata(default(string)));
public int Type
{
get { return (int) GetValue(TypeProperty ); }
set { SetValue(TypeProperty , value); }
}
}
Hope it helps ;)

Bind Button IsEnabled property to DataTemplate items state and one additional condition

I have an object with editable parameters collection which are bound as a ItemsSource to ItemsControl, and a property which checks if all parameter values are ok. This property bound to button's IsEnabled.
I also want to disable the button when any of textbox has validation error (Validation.HasError == true).
Thanks in advance.
XAML:
<Window x:Class="MyWPFTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<StackPanel>
<ItemsControl ItemsSource="{Binding Path=MyObject.Parameters}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Path=Name}"></TextBlock>
<TextBox Text="{Binding Path=Value, UpdateSourceTrigger=PropertyChanged}"></TextBox>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<Button IsEnabled="{Binding Path=MyObject.IsParametersOkay}">OK</Button>
</StackPanel>
</Window>
Code:
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows;
namespace MyWPFTest
{
public partial class MainWindow : Window
{
ObjectWithParameters _MyObject = new ObjectWithParameters();
public ObjectWithParameters MyObject { get { return _MyObject; } }
public MainWindow()
{
InitializeComponent();
DataContext = this;
}
}
public class ObjectWithParameters : INotifyPropertyChanged
{
ObservableCollection<Parameter> _Parameters = new ObservableCollection<Parameter>();
public ObservableCollection<Parameter> Parameters { get { return _Parameters; } }
public event PropertyChangedEventHandler PropertyChanged;
public ObjectWithParameters()
{
var p1 = new Parameter("Parameter 1", 0); p1.PropertyChanged += ParameterChanged; Parameters.Add(p1);
var p2 = new Parameter("Parameter 2", 0); p2.PropertyChanged += ParameterChanged; Parameters.Add(p2);
}
void ParameterChanged(object sender, PropertyChangedEventArgs e)
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("IsParametersOkay"));
}
public bool IsParametersOkay
{
get { return Parameters.FirstOrDefault(p => p.Value < 0) == null; }
}
}
public class Parameter : INotifyPropertyChanged
{
double val;
public double Value
{
get { return val; }
set { val = value; if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("Value")); }
}
public string Name { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
public Parameter(string name, double value) { Name = name; Value = value; }
}
}

Check out MultiTriggers.
<Style.Triggers>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Background" Value="#EEEEEE" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasItems" Value="false" />
<Condition Property="Width" Value="Auto" />
</MultiTrigger.Conditions>
<Setter Property="MinWidth" Value="120"/>
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="HasItems" Value="false" />
<Condition Property="Height" Value="Auto" />
</MultiTrigger.Conditions>
<Setter Property="MinHeight" Value="95"/>
</MultiTrigger>
</Style.Triggers>

This is the way I solved the problem. May be it's not a very elegant solution, but it works.
I added a new property IsFormOkay to MainWindow class, which checks both controls and parameters validity. Then I bound Button.IsEnabled to this property and added TextChanged event for TextBox to notify about IsFormOkay.
Here is code added to MainWindow:
public event PropertyChangedEventHandler PropertyChanged;
public bool IsFormOkay { get { return IsValid(Items) && MyObject.IsParametersOkay; } }
public bool IsValid(DependencyObject obj)
{
if (Validation.GetHasError(obj)) return false;
for (int i = 0, n = VisualTreeHelper.GetChildrenCount(obj); i < n; i++)
{
DependencyObject child = VisualTreeHelper.GetChild(obj, i);
if (!IsValid(child)) return false;
}
return true;
}
private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs("IsFormOkay"));
}
And changes to XAML:
<StackPanel>
<ItemsControl x:Name="Items" ItemsSource="{Binding Path=MyObject.Parameters}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Path=Name}" />
<TextBox TextChanged="TextBox_TextChanged" Text="{Binding Path=Value, UpdateSourceTrigger=PropertyChanged}" />
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<Button IsEnabled="{Binding Path=IsFormOkay}" Content="OK" />
</StackPanel>