Develop Reference

Color the row in combobox?

I'm having trouble with finding the solution for the problem, namely I had an idea to color each row/column of combobox with different colors, depending on the area, but i cannot find any clues or hints or instructions to do so. the app is pretty simple
<ComboBox x:Name="comboBox1" HorizontalAlignment="Left" Margin="84,70,0,0" VerticalAlignment="Top" Width="230"/>
this is my XAML combobox, which i fill from the code:
SortedList<int, string> AreaList = new SortedList<int, string>();
AreaList.Add(1, "Agriculture");
AreaList.Add(2, "Forestry");
AreaList.Add(3, "Fruits");
AreaList.Add(4, "Food");
AreaList.Add(5, "Metals");
AreaList.Add(6, "Mining");
AreaList.Add(7, "Electricity");
AreaList.Add(8, "Building Contracts");
AreaList.Add(9, "Transport");
AreaList.Add(10, "Alcohol");
AreaList.Add(11, "Information Technologies");
AreaList.Add(12, "Health And Social Services");
AreaList.Add(13, "Art and Entertainement");
AreaList.Add(14, "Hospitality Business");
AreaList.Add(15, "Education");
AreaList.Add(16, "Real Estate");
AreaList.Add(17, "Sales");
AreaList.Add(18, "Architecture");
AreaList.Add(19, "Engineering");
AreaList.Add(20, "Wholesale");
AreaList.Add(21, "Other");
comboBox1.ItemsSource = AreaList.ToList();
comboBox1.SelectedValuePath = "Key";
comboBox1.DisplayMemberPath = "Value";
each of these items have their color in another window, but i would like to show those colors in the combobox, the background of "Agriculture" row/column should be green etc.
Is there a solution to this, or do i have to redo it all over?

You could use an ItemContainerStyle with a DataTrigger for each value that maps to a colour:
<ComboBox x:Name="comboBox1">
<ComboBox.ItemContainerStyle>
<Style TargetType="ComboBoxItem">
<Style.Triggers>
<DataTrigger Binding="{Binding Value}" Value="Agriculture">
<Setter Property="Background" Value="Green" />
</DataTrigger>
<DataTrigger Binding="{Binding Value}" Value="Forestry">
<Setter Property="Background" Value="Red" />
</DataTrigger>
<!-- and so on-->
</Style.Triggers>
</Style>
</ComboBox.ItemContainerStyle>
</ComboBox>
You may also want to read this:
Changing the background colour of a ComboBox in WPF: https://blog.magnusmontin.net/2014/04/30/changing-the-background-colour-of-a-combobox-in-wpf-on-windows-8/

You can make use of ItemContainerStyle and Converter
public class StringToColorConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
if (((KeyValuePair<int, string>)value).Value.ToString() == "Agriculture")
return Brushes.Green;
//and so on or other ways to get the color
return Brushes.Transparent;
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
and XAML goes as follows,
<Window.Resources>
<local:StringToColorConverter x:Key="StringToColorConverter"/>
</Window.Resources>
<Grid >
<ComboBox x:Name="comboBox1" HorizontalAlignment="Left" Margin="84,70,0,0" VerticalAlignment="Top" Width="230">
<ComboBox.ItemContainerStyle>
<Style TargetType="ComboBoxItem">
<Setter Property="Background" Value="{Binding Converter={StaticResource StringToColorConverter}}">
</Setter>
</Style>
</ComboBox.ItemContainerStyle>
</ComboBox>
</Grid>

Databinding property from wpf style to viewmodel

I have an application that uses two separate projects. One is for the main executable which contains my ViewModels and the other is to control the theme/style of the application.
In the theme project, I have customized the DataGridColumnHeader's Style to include a CheckBox. Now how do I databind the CheckBoxes to my ViewModel?
My theme xaml
<Style x:Key='PlottableFilteringColumnHeaderStyle' TargetType='{x:Type primitives:DataGridColumnHeader}'>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type primitives:DataGridColumnHeader}">
<Grid>
<themes:DataGridHeaderBorder x:Name='HeaderBorder'>
<Grid x:Name="GridColumnHeader">
<StackPanel x:Name="argStackPanel">
<CheckBox x:Name="argCheckBox" Content="Enable Arg" Style="{DynamicResource ResourceKey=DefaultCheckBox}" />
</StackPanel>
</Grid>
</themes:DataGridHeaderBorder>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I am then using MultiBinding for the argCheckBox
public class HeaderArgConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
string headerText = values[0] as string;
if (!String.IsNullOrWhiteSpace(headerText))
{
FrameworkElement targetElement = values[1] as FrameworkElement;
DataGridColumnHeader header = targetElement.TemplatedParent as DataGridColumnHeader;
string columnName = header.DataContext != null ? header.DataContext.ToString() : "";
var argNumber = System.Text.RegularExpressions.Regex.Match(columnName.Split(':')[0], #"\d+$").Value; // use the header text to determine which arg number
Binding binding = new Binding("SelectedViewModel.EnableArg" + argNumber);
binding.Source = Window.DataContextProperty; // This is what I am unsure about
(targetElement as CheckBox).SetBinding(CheckBox.IsCheckedProperty, binding);
}
}
}
I keep getting 'BindingExpression path error: property not found on 'object'' error. Any ideas on how to fix this or if there is a better way to do this?

Deselect selected item in wpf tree view (MVVM)

I am using a WPF treeview, when i click on a node\item once it gets selected. When the user clicks on the selected node the second time i want this node\item to get deselected i.e. i should be able to get the event. IsSelected is not called if i click on the selected node\item that is already selected. How do i get it to work?
<TreeView Grid.Column="0" Grid.Row="1" ItemsSource="{Binding source}" Name="mytreeview">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsExpanded" Value="{Binding IsExpanded, Mode=TwoWay}" />
<Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
<Setter Property="FontWeight" Value="Normal" />
<Style.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter Property="FontWeight" Value="Bold" />
</Trigger>
</Style.Triggers>
</Style>
</TreeView.ItemContainerStyle>
<TreeView.ItemTemplate>
<HierarchicalDataTemplate ItemsSource="{Binding Children}">
<TextBlock Text="{Binding displaytext}"/>
</HierarchicalDataTemplate>
</TreeView.ItemTemplate>
</TreeView>
and in my view model i have
public bool IsSelected
{
get
{
return _isSelected;
}
set
{
if (value != _isSelected)
{
_isSelected = value;
if (_isSelected)
{
//my logic
}
this.OnPropertyChanged("IsSelected");
}
}
}

if (value != _isSelected)
Assuming that the UI is even trying to set something, that line is blocking your toggle logic. Something like this should fix at least that part.
set
{
if (value != _isSelected)
{
_isSelected = value;
this.OnPropertyChanged("IsSelected");
}
else if(_isSelected)
{
IsSelected = false;
}
}
Otherwise the UI is checking the selection before setting the value and you'll need to handle it through some other user interaction like handling deselection on click.

I know this is a bit late but I've recently had the same requirement (i.e. unselecting a selected TreeViewItem on the second click) and I solved it by declaring an event handler for the 'MouseLeftButtonUp' event in a 'Style' entry for the ItemContainerStyle of the TreeView as follows:
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<EventSetter Event="MouseLeftButtonUp" Handler="TreeViewItem_MouseLeftButtonUp"/>
</Style>
</TreeView.ItemContainerStyle>
The event handler in the code behind was as follows:
private TreeViewItem prevTVI;
private void TreeViewItem_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
TreeViewItem tvi = (TreeViewItem)sender;
if (tvi == this.prevTVI)
{
this.prevTVI = null;
if (tvi.IsSelected)
tvi.IsSelected = false;
}
else
this.prevTVI = tvi;
e.Handled = true;
}
Now, I would like to ask if anyone thinks this approach breaks the MVVM pattern? I personally don't think so as the event handler is only concerned with the View and its objects not anything else but I would like to hear what others have to say, especially if someone has an alternative.

The IsSelected property is only changed when you select a new item. Clicking on the same item twice will normally have no effect. You would need to register the MouseDown event on the TreeView, and then force the item to be deselected in the code-behind.

Separate text in a Textbox with a drawn line?

So here it goes, I making a c# project in wpf and im stuck at trying to make a text box with a line that separates text.
At the moment i got the textbox like this:
Instead of using "-------" i want to make a predefined line in the textbox. Is this possible ?
Agg. The textbox is editable in runtime
The drawn line should have the properties:
It should not be edit able !
It shouldn't only be an empty line
It should be a visible line that has the width line.width = box.width !

If you don't need a full textbox implementation then this might help. It's got real issues with not showing the cursor ect but might give you a start.
first add the following converter to your project.
public class TextLineConverter : MarkupExtension, IValueConverter
{
static TextLineConverter converter;
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
string[] results = null;
string newText = value as string;
if (newText != null)
{
results = newText.Split('\r');
if (results.Length > 0)
for (int i = 0; i < results.Length; i++)
if (results[i].Length > 0)
if (results[i][0] == '\n')
results[i] = results[i].Substring(1, results[i].Length - 1);
}
return results;
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new NotImplementedException();
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
if (converter == null) converter = new TextLineConverter();
return converter;
}
public TextLineConverter()
{
}
}
And the following style.
<Style TargetType="TextBox">
<Style.Resources>
<Style TargetType="ListViewItem">
<Setter Property="Margin" Value="0"/>
<Setter Property="Padding" Value="0"/>
<Setter Property="IsEnabled" Value="False"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate>
<Border BorderThickness="0,0,0,2" BorderBrush="Black" >
<ContentPresenter Content="{Binding}" />
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Style.Resources>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="TextBox">
<ListView Focusable="False" ItemsSource="{Binding Text, Converter={local:TextLineConverter}, UpdateSourceTrigger=PropertyChanged, RelativeSource={RelativeSource TemplatedParent}}"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

On rereading your question, i believe that the best way to do what you want is to create your own user-control that has an attribute specifically for this. Do some research on C# User Controls and perhaps you'll find out how to do this.

Get an instance of TabItem's ContentTemplate

I have a TabControl tied to a collection of items where each item is supposed to be represented by a normal TabItem which hosts a user control, like so:
<TabControl x:Name="Items"
ItemsSource="{Binding ElementName=This,Path=Files}">
<TabControl.ItemContainerStyle>
<Style TargetType="{x:Type TabItem}">
<Setter Property="Header" Value="{Binding Path=Name}" />
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate DataType="{x:Type App:MyContext}">
<App:Task x:Name="task" Image="{Binding Path=Image}" />
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
</TabControl.ItemContainerStyle>
</TabControl>
The ItemsSource is bound to an ObservableCollection<MyContext>.
I would like to get to each and every App:Task generated for each of my MyContext instances like so (or similar):
foreach (var file in Files)
{
var container = Items.ItemContainerGenerator.ContainerFromItem(file) as TabItem;
if (container == null) continue;
var task = container.Content as Task;
if (task == null) return;
// ...
}
But the container.Content is MyContext not Task. So I figured I should use:
var task = container.ContentTemplate.FindName("task") as Task;
But this throws an exception because at this point the ContentTemplate does not seem to have been applied yet. How can I force it or get what I want in any other way?

Why do you need the UserControl in the first place?
If you need to access something you haven't bound enough properties on your items to the UserControls.