Develop Reference

Must have non-null value for 'Binding' problem

I have made a custom Control in WPF which is a star rating. When there are 5 stars, these should be golden.
<UserControl x:Class="Lama.Wpf.Controls.RatingControl"
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:controls="clr-namespace:Lama.Wpf.Controls"
mc:Ignorable="d">
<Grid>
<Grid.Resources>
<ControlTemplate x:Key="RatingTemplate" TargetType="{x:Type ToggleButton}">
<Viewbox>
<Path Name="star" Fill="White" Opacity="0.2"
Data="F1 M 145.637,174.227L 127.619,110.39L 180.809,70.7577L 114.528,68.1664L 93.2725,5.33333L 70.3262,67.569L 4,68.3681L 56.0988,109.423L 36.3629,172.75L 91.508,135.888L 145.637,174.227 Z" />
</Viewbox>
<ControlTemplate.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Property="IsChecked" Value="True" />
<Condition
Binding="{Binding Rating, RelativeSource={RelativeSource FindAncestor, AncestorType=controls:RatingControl}}"
Value="5" />
</MultiDataTrigger.Conditions>
<MultiDataTrigger.Setters>
<Setter TargetName="star" Property="Fill" Value="Gold" />
<Setter TargetName="star" Property="Opacity" Value="1" />
</MultiDataTrigger.Setters>
</MultiDataTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Grid.Resources>
<Grid.ColumnDefinitions>
<ColumnDefinition />
<ColumnDefinition />
<ColumnDefinition />
<ColumnDefinition />
<ColumnDefinition />
</Grid.ColumnDefinitions>
<ToggleButton Grid.Column="0" Tag="1" Padding="2" Template="{StaticResource RatingTemplate}"
Click="ClickEventHandler" />
<ToggleButton Grid.Column="1" Tag="2" Padding="2" Template="{StaticResource RatingTemplate}"
Click="ClickEventHandler" />
<ToggleButton Grid.Column="2" Tag="3" Padding="2" Template="{StaticResource RatingTemplate}"
Click="ClickEventHandler" />
<ToggleButton Grid.Column="3" Tag="4" Padding="2" Template="{StaticResource RatingTemplate}"
Click="ClickEventHandler" />
<ToggleButton Grid.Column="4" Tag="5" Padding="2" Template="{StaticResource RatingTemplate}"
Click="ClickEventHandler" />
</Grid>
</UserControl>
public partial class RatingControl
{
private const int Max = 5;
public static readonly DependencyProperty RatingProperty = DependencyProperty.Register(nameof(Rating),
typeof(int),
typeof(RatingControl),
new FrameworkPropertyMetadata(0, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
RatingChanged));
public int Rating
{
get => (int)GetValue(RatingProperty);
set
{
if (value < 0)
{
SetValue(RatingProperty, 0);
}
else if (value > Max)
{
SetValue(RatingProperty, Max);
}
else
{
SetValue(RatingProperty, value);
}
}
}
public RatingControl()
{
InitializeComponent();
}
private static void RatingChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
{
var item = sender as RatingControl;
var newVal = (int)e.NewValue;
var children = ((Grid)(item.Content)).Children;
ToggleButton button;
for (var i = 0; i < newVal; i++)
{
button = children[i] as ToggleButton;
if (button != null)
button.IsChecked = true;
}
for (var i = newVal; i < children.Count; i++)
{
button = children[i] as ToggleButton;
if (button != null)
button.IsChecked = false;
}
}
private void ClickEventHandler(object sender, RoutedEventArgs args)
{
var button = sender as ToggleButton;
if (button == null)
{
return;
}
var newValue = int.Parse(button.Tag.ToString());
Rating = newValue;
}
}
If I run this, I get this exception:
InvalidOperationException: Must have non-null value for 'Binding'.
Do I bind something wrong inside my condition? Because if I remove the Rating-Binding, it works, but I don't see my mistake here.

There are multiple issues in your Condition bindings:
The first binding in the MultiDataTrigger uses a Condition that sets Property, which is wrong.
For a MultiDataTrigger, each condition in the collection must set both the Binding and Value properties. For more information, see Binding.
Set the Binding property using a RelativeSource binding to Self instead.
<Condition Binding="{Binding IsChecked, RelativeSource={RelativeSource Self}}" Value="True"/>
The second binding to Rating is faulty, since it would only ever set any star to be golden and opaque if the rating is exactly five stars. So no stars are selected for any other rating.
In order resolve these issues, you can use a simple Trigger on the IsChecked property.
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="True">
<Setter TargetName="star" Property="Fill" Value="Gold" />
<Setter TargetName="star" Property="Opacity" Value="1" />
</Trigger>
</ControlTemplate.Triggers>
If it is really your requirement to only make the stars golden and opaque if the rating is exactly 5, then you could correct the MultiDataTrigger as stated above:
<ControlTemplate.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding IsChecked, RelativeSource={RelativeSource Self}}" Value="True"/>
<Condition Binding="{Binding Rating, RelativeSource={RelativeSource FindAncestor, AncestorType=controls:RatingControl}}" Value="5"/>
</MultiDataTrigger.Conditions>
<MultiDataTrigger.Setters>
<Setter TargetName="star" Property="Fill" Value="Gold" />
<Setter TargetName="star" Property="Opacity" Value="1" />
</MultiDataTrigger.Setters>
</MultiDataTrigger>
</ControlTemplate.Triggers>
Another note on value coercion. As #Clemens stated in the comments, setting a property in XAML e.g. like below will bypass your setter and
call SetValue directly. Your setter should only call SetValue as the behavior will differ otherwise when setting properties in XAML or through the property.
<local:RatingControl Rating="{Binding SomeProperty}"/>
Instead of the checks in the setter, you can specify a value coercion callback in the dependency property declaration.
public static readonly DependencyProperty RatingProperty = DependencyProperty.Register(
nameof(Rating), typeof(int), typeof(RatingControl), new FrameworkPropertyMetadata(
0, FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, RatingChanged, CoerceRating));
Then create a CoerceRating method that contains your checks and returns the corresponding values.
private static object CoerceRating(DependencyObject d, object baseValue)
{
var value = (int)baseValue;
if (value < 0)
{
return 0;
}
if (value > Max)
{
return Max;
}
return value;
}
Finally, remove all checks from the setter of Rating.
public int Rating
{
get => (int)GetValue(RatingProperty);
set => SetValue(RatingProperty, value);
}
The value coercion callback will automatically be called, when the property is set through SetValue and therefore ensure that the Rating value is within the valid interval.

Change button appearance/icon

I want to change the icon on my button. Here is the xaml of my button:
<Button Name="InitPurgeBtn" Click="InitPurgeClick">
<Rectangle Width="35" Height="45" Margin="0,0,0,0">
<Rectangle.Fill>
<VisualBrush Stretch="Fill" Visual="{StaticResource InitIcon}" />
</Rectangle.Fill>
</Rectangle>
</Button>
The probleme is I don't know how to acces the Visual property of the Rectangle of my button in my controller to change "InitIcon" by "PurgeIcon"
All my icon are implement in xaml:
<Viewbox x:Key="ExtinctionIcon" Stretch="Uniform" x:Shared="False">
<Canvas Width="76" Height="76" Clip="F1 M 0,0L 76,0L 76,76L 0,76L 0,0">
<Path Width="40" Height="40" Stretch="Fill" Fill="{Binding Foreground,
RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Button}}"
Data="M15,24H17V22H15M16.56,{...}24H13V22H11M7,24H9V22H7V24Z"/>
</Canvas>
</Viewbox>
Edit :
I change my button and he is like this now :
<Button Name="InitBtn" Style="{StaticResource RoundButton}" Width="70" Height="70"
Click="InitPurgeClick" Content="{StaticResource InitIcon}">
</Button>
I want to change the icon in my code so I try to set Content property like this :
InitBtn.Content = "{StaticResource ExtinctionIcon}";
But this way just replace my icon with the string "StaticResource.."

Updated to reflect new information
You updated your question with some new information that changes things a lot.
Since you are trying to update Button.Content in code, you won't be able to use the MarkupExtension. MarkupExtensions (the stuff inside { } in the XAML) are only evaluated when the view is initially created. After that, they behave just like regular strings, so trying to set one in code won't work.
To set the value in code, you will need to manually do what the MarkupExtension is doing; find the resource by name, and set the value directly. You can do this with the following code (assuming a reference to InitPurgeBtn).
InitPurgeBtn.Content = InitPurgeBtn.FindResource("ExtinctionIcon");
Previous Answer
You should be able to add your icon to the Content of the Button directly, as it seems to be defined as a resource somewhere (because of the x:Key attribute). Your code doesn't show where exactly that is though, so I can't grantee this will work without some modification.
<Button Name="InitPurgeBtn"
Width="100"
Height="40"
Content="{StaticResource ExtinctionIcon}" />
In order for that to work the ExtinctionIcon resource will have to be defined someplace accessible to the button, meaning either in an ancestor of the button, or in App.xaml.
The fact that the resource is defined with x:Shared="false" seems to indicate that it was designed to be used in exactly this way, as that is required for visual elements that can possibly be hosted in multiple places simultaneously.
Alternatively, you could just copy and embed the icon directly in to the button.
<Button Name="InitPurgeBtn"
Click="InitPurgeClick">
<Viewbox Stretch="Uniform">
<Canvas Width="76"
Height="76"
Clip="F1 M 0,0L 76,0L 76,76L 0,76L 0,0">
<Path Width="40"
Height="40"
Stretch="Fill"
Fill="{Binding Foreground,
RelativeSource={RelativeSource
Mode=FindAncestor,
AncestorType=Button}}"
Data="M15,24H17V22H15M16.56,{...}24H13V22H11M7,24H9V22H7V24Z"/>
</Canvas>
</Viewbox>
</Button>

You may use Content property.
<Button Name="InitPurgeBtn" Width="100" Height="40">
<Button.Content>
<Image Source=".\Icon.PNG"/>
</Button.Content>
</Button>

If you just want a single (xaml) icon, you can bind the content property of your button to your icon resource.
The control below gives an enhanced display - a xaml icon plus a text caption, including two colours for the icon and support for disabled state.
MyXamlIconHost.cs
public enum CaptionPosition { None, ToLeftOfIcon, AboveIcon, ToRightOfIcon, BelowIcon }
public enum IconSize { Small, Medium, Large, XLarge, XxLarge }
public class myXamlIconHost : Control
{
private static readonly Brush DefaultForeground = new SolidColorBrush(Color.FromRgb(32,32,32));
private static readonly Brush DefaultHighlight = Brushes.DarkOrange;
private static readonly Brush DefaultDisabledForeground = new SolidColorBrush(Color.FromRgb(192, 192, 192));
private static readonly Brush DefaultDisabledHighlight = new SolidColorBrush(Color.FromRgb(128, 128, 128));
static myXamlIconHost()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(myXamlIconHost), new FrameworkPropertyMetadata(typeof(myXamlIconHost)));
}
public FrameworkElement XamlIcon
{
get { return (FrameworkElement)GetValue(XamlIconProperty); }
set { SetValue(XamlIconProperty, value); }
}
public static readonly DependencyProperty XamlIconProperty =
DependencyProperty.Register("XamlIcon", typeof(FrameworkElement), typeof(myXamlIconHost), new PropertyMetadata(null));
public IconSize IconSize
{
get { return (IconSize)GetValue(IconSizeProperty); }
set { SetValue(IconSizeProperty, value); }
}
public static readonly DependencyProperty IconSizeProperty =
DependencyProperty.Register("IconSize", typeof(IconSize), typeof(myXamlIconHost), new PropertyMetadata(IconSize.Medium));
public string Caption
{
get { return (string)GetValue(CaptionProperty); }
set { SetValue(CaptionProperty, value); }
}
public static readonly DependencyProperty CaptionProperty =
DependencyProperty.Register("Caption", typeof(string), typeof(myXamlIconHost), new PropertyMetadata(null));
public CaptionPosition CaptionPosition
{
get { return (CaptionPosition)GetValue(CaptionPositionProperty); }
set { SetValue(CaptionPositionProperty, value); }
}
public static readonly DependencyProperty CaptionPositionProperty =
DependencyProperty.Register("CaptionPosition", typeof(CaptionPosition), typeof(myXamlIconHost), new PropertyMetadata(CaptionPosition.ToRightOfIcon));
public Brush StandardForeground
{
get { return (Brush)GetValue(StandardForegroundProperty); }
set { SetValue(StandardForegroundProperty, value); }
}
public static readonly DependencyProperty StandardForegroundProperty =
DependencyProperty.Register("StandardForeground", typeof(Brush), typeof(myXamlIconHost), new PropertyMetadata(DefaultForeground));
public Brush StandardHighlight
{
get { return (Brush)GetValue(StandardHighlightProperty); }
set { SetValue(StandardHighlightProperty, value); }
}
public static readonly DependencyProperty StandardHighlightProperty =
DependencyProperty.Register("StandardHighlight", typeof(Brush), typeof(myXamlIconHost), new PropertyMetadata(DefaultHighlight));
public Brush DisabledForeground
{
get { return (Brush)GetValue(DisabledForegroundProperty); }
set { SetValue(DisabledForegroundProperty, value); }
}
public static readonly DependencyProperty DisabledForegroundProperty =
DependencyProperty.Register("DisabledForeground", typeof(Brush), typeof(myXamlIconHost), new PropertyMetadata(DefaultDisabledForeground));
public Brush DisabledHighlight
{
get { return (Brush)GetValue(DisabledHighlightProperty); }
set { SetValue(DisabledHighlightProperty, value); }
}
public static readonly DependencyProperty DisabledHighlightProperty =
DependencyProperty.Register("DisabledHighlight", typeof(Brush), typeof(myXamlIconHost), new PropertyMetadata(DefaultDisabledHighlight));
}
// ==============================================================================================================================================
public class myXamlIconSizeConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
const int defaultSize = 24;
if (!(value is IconSize))
return defaultSize;
var iconSizeValue = (IconSize)value;
switch (iconSizeValue)
{
case IconSize.Small:
return defaultSize * 2 / 3;
case IconSize.Large:
return defaultSize * 3 / 2;
case IconSize.XLarge:
return defaultSize * 2;
case IconSize.XxLarge:
return defaultSize * 5 / 2;
default:
return defaultSize;
}
}
public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
{
return null;
}
}
MyXamlIconHost.xaml
<Style TargetType="{x:Type ctrl:myXamlIconHost}">
<Setter Property="Focusable" Value="False" />
<Setter Property="HorizontalAlignment" Value="Center" />
<Setter Property="Padding" Value="0" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ctrl:myXamlIconHost}">
<Grid Margin="{TemplateBinding Padding}">
<Grid.Resources>
<ctrl:myXamlIconSizeConverter x:Key="IconSizeConverter" />
</Grid.Resources>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBlock x:Name="PART_CaptionTextBlock"
Grid.Row="1"
Grid.Column="0"
Margin="8,0,8,0"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Foreground="{TemplateBinding StandardForeground}"
Text="{TemplateBinding Caption}" />
<!-- Set DataContext to "self" so that the Xaml Icon item can bind to the Foreground and BorderBrush properties -->
<ContentControl x:Name="PART_IconPresenter"
Grid.Row="1"
Grid.Column="1"
Width="{TemplateBinding IconSize,
Converter={StaticResource IconSizeConverter}}"
Height="{TemplateBinding IconSize,
Converter={StaticResource IconSizeConverter}}"
HorizontalAlignment="Center"
VerticalAlignment="Center"
BorderBrush="{TemplateBinding StandardHighlight}"
Content="{TemplateBinding XamlIcon}"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
Focusable="False"
Foreground="{TemplateBinding StandardForeground}" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsEnabled" Value="False">
<Setter TargetName="PART_CaptionTextBlock" Property="Foreground" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=DisabledForeground}" />
<Setter TargetName="PART_IconPresenter" Property="BorderBrush" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=DisabledHighlight}" />
<Setter TargetName="PART_IconPresenter" Property="Foreground" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=DisabledForeground}" />
</Trigger>
<Trigger Property="CaptionPosition" Value="None">
<Setter TargetName="PART_CaptionTextBlock" Property="Visibility" Value="Collapsed" />
</Trigger>
<Trigger Property="CaptionPosition" Value="ToLeftOfIcon">
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Column" Value="0" />
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Row" Value="1" />
<Setter TargetName="PART_CaptionTextBlock" Property="Margin" Value="8,0,8,0" />
</Trigger>
<Trigger Property="CaptionPosition" Value="ToRightOfIcon">
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Column" Value="2" />
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Row" Value="1" />
<Setter TargetName="PART_CaptionTextBlock" Property="Margin" Value="8,0,8,0" />
</Trigger>
<Trigger Property="CaptionPosition" Value="AboveIcon">
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Column" Value="1" />
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Row" Value="0" />
<Setter TargetName="PART_CaptionTextBlock" Property="Margin" Value="8,0,8,4" />
</Trigger>
<Trigger Property="CaptionPosition" Value="BelowIcon">
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Column" Value="1" />
<Setter TargetName="PART_CaptionTextBlock" Property="Grid.Row" Value="2" />
<Setter TargetName="PART_CaptionTextBlock" Property="Margin" Value="8,4,8,0" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
<Setter Property="VerticalAlignment" Value="Center" />
</Style>
Example Usage
<Window ... >
<Window.Resources>
<Grid x:Key="TestIcon" x:Shared="False" Background="Transparent">
<Path Stretch="Fill" Data=" M 0,0 M 100,100 M 0,0 L 0,100 L 100,100 L 100,60 L 90,60 L 90,90 L 10,90 L 10,10 L 90,10 L 90,40 L 100,40 L 100,0 z" Fill="{ Binding Foreground, FallbackValue=Cyan}"/>
<Path Stretch="Fill" Data=" M 0,0 M 100,100 M 70,45 L 100,45 L 100,55 L 70,55 z" Fill="{ Binding BorderBrush, FallbackValue=Magenta}"/>
</Grid>
</Window.Resources>
<Button HorizontalAlignment="Center" VerticalAlignment="Center">
<Border Background="LightBlue">
<ctrls:myXamlIconHost Caption="The Caption" XamlIcon="{StaticResource TestIcon}" IconSize="XxLarge" Padding="20" />
</Border>
</Button>
</Window>

WPF Custom Base Window Class and Style

I have a an app that will open many windows, and I want all windows to look the same. I am overriding the default Windows window chrome style and making my own, so any new window that is opened (excluding messageboxes) should have the same window style. However, no matter what I seem to try it does not work. I can get it to work with one window, but when I want to make it a global style it always crashes or simply doesn't work as it should.
Here is my code:
WindowBaseStyle.xaml
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:MyProject.Styles"
xmlns:views="clr-namespace:Myproject.Views">
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="GlobalStyles.xaml" />
</ResourceDictionary.MergedDictionaries>
<Style TargetType="{x:Type views:WindowBase}" BasedOn="{StaticResource {x:Type Window}}">
<Setter Property="AllowsTransparency" Value="False" />
<Setter Property="BorderBrush" Value="Red" />
<Setter Property="BorderThickness" Value="1" />
<Setter Property="WindowState" Value="Normal" />
<Setter Property="WindowStyle" Value="SingleBorderWindow" />
<Setter Property="WindowChrome.WindowChrome">
<Setter.Value>
<WindowChrome CaptionHeight="30"
UseAeroCaptionButtons="False"/>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type views:WindowBase}">
<Border BorderBrush="Blue" BorderThickness="1" SnapsToDevicePixels="True">
<DockPanel Background="White" LastChildFill="True" >
<Grid Background="Blue" DockPanel.Dock="Top">
<StackPanel HorizontalAlignment="Left" Orientation="Horizontal" VerticalAlignment="Center">
<Button Name="PART_SystemMenuButton" Command="{Binding MenuCommand}" Style="{DynamicResource SystemIconButton}">
<Image Height="16" Width="16" Source="/Resources/icon.png" Stretch="Fill"/>
</Button>
<Viewbox Height="16" HorizontalAlignment="Stretch" Margin="14,2,0,0" >
<TextBlock FontSize="12" Foreground="White" Text="{Binding Title,RelativeSource={RelativeSource FindAncestor,AncestorType=Window}}" />
</Viewbox>
</StackPanel>
<StackPanel Orientation="Horizontal" WindowChrome.IsHitTestVisibleInChrome="True">
<Button x:Name="PART_MinimizeButton" Command="{Binding MinimizeCommand}" Height="30" Margin="0,0,0,0" ToolTip="Minimize" Width="45">
<Image Source="/Resources/minimize.png" Stretch="None" />
<Button.Style>
<Style TargetType="{x:Type Button}">
<Setter Property="Background" Value="#0079CB" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border Background="{TemplateBinding Background}">
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="#64AEEC"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
<Button x:Name="PART_MaximizeButton" Command="{Binding MaximizeCommand}" Height="30" Margin="0,0,0,0" Width="45">
<Image>
<Image.Style>
<Style TargetType="{x:Type Image}">
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}, Path=WindowState}" Value="Normal">
<Setter Property="Source" Value="/Resources/maximize.png" />
<Setter Property="Stretch" Value="None" />
</DataTrigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}, Path=WindowState}" Value="Maximized">
<Setter Property="Source" Value="/Resources/unmaximize.png" />
<Setter Property="Stretch" Value="None" />
</DataTrigger>
</Style.Triggers>
</Style>
</Image.Style>
</Image>
<Button.Style>
<Style TargetType="{x:Type Button}">
<Setter Property="Background" Value="#0079CB" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border Background="{TemplateBinding Background}">
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="#64AEEC"/>
</Trigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}, Path=WindowState}" Value="Normal">
<Setter Property="ToolTip" Value="Maximize" />
</DataTrigger>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}, Path=WindowState}" Value="Maximized">
<Setter Property="ToolTip" Value="Restore Down" />
</DataTrigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
<Button x:Name="PART_CloseButton" Command="{Binding CloseCommand}" Height="30" Margin="0,0,0,0" ToolTip="Close" Width="45" >
<Image Source="/Resources/close.png" Stretch="None" />
<Button.Style>
<Style TargetType="{x:Type Button}">
<Setter Property="Background" Value="#0079CB" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border Background="{TemplateBinding Background}">
<ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="Red"/>
</Trigger>
</Style.Triggers>
</Style>
</Button.Style>
</Button>
</StackPanel>
</StackPanel>
</Grid>
<!-- this ContentPresenter automatically binds to the content of the window -->
<ContentPresenter />
</DockPanel>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
WindowBase.cs
using System;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Interop;
namespace MyProject.Views
{
[TemplatePart(Name = "PART_MinimizeButton", Type = typeof(Button))]
[TemplatePart(Name = "PART_MaximizeButton", Type = typeof(Button))]
[TemplatePart(Name = "PART_CloseButton", Type = typeof(Button))]
[TemplatePart(Name = "PART_SystemMenuButton", Type = typeof(Button))]
public class WindowBase: Window
{
static WindowBase()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(CustomWindow), new FrameworkPropertyMetadata(typeof(CustomWindow)));
}
public WindowBase()
{
Loaded += (sender, evnt) =>
{
var MinimizeButton = (Button)Template.FindName("PART_MinimizeButton", this);
var MaximizeButton = (Button)Template.FindName("PART_MaximizeButton", this);
var CloseButton = (Button)Template.FindName("PART_CloseButton", this);
var SystemMenuButton = (Button)Template.FindName("PART_SystemMenuButton", this);
MinimizeButton.Click += (s, e) => WindowState = WindowState.Minimized;
MaximizeButton.Click += (s, e) => WindowState = WindowState == WindowState.Maximized ? WindowState.Normal : WindowState.Maximized;
CloseButton.Click += (s, e) => Close();
SystemMenuButton.Click += (s, e) => SystemCommands.ShowSystemMenu(this, GetMousePosition());
};
}
}
}
Window1.xaml
<local:WindowBase x:Class="MyProject.Views.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:MyProject.Views"
Height="750"
Width="1125">
<Grid>
</Grid>
</local:WindowBase>
Window1.xaml.cs
using System.Windows;
namespace MyProject.Views
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1: WindowBase
{
public Window1()
{
InitializeComponent();
}
}
}
I am overall following the MVVM pattern, and for the most part from all the articles and videos I have looked at online, they all follow this basic approach and they say it all works, but I can't seem to get it to work.
An additional note is that whenever I add my custom window control to the Window1.xaml file, it breaks the designer and says it is "Invalid Markup"
Also note I added my "WindowBaseStyle" resource dictionary to the App.xaml file as a merged resource dictionary.
Any help is greatly appreciated!! Thanks

Ok, as we discussed in the comments, it seems like the fastest solution to the problem you described is to use a StaticResource to get the window's style from a resource dictionary (or create an implicit style for windows.) I questioned the role of CustomWindow because I thought that might be causing problems with your default style override. (Remember: if you go the lookless control route and try to use the DefaultStyleKeyProperty override, you have to do this on every subclass of that control.)
However, I think doing something like this will get you reusable plumbing for multiple windows driven by viewmodels...
PopupHost
A class that would derive from your customized window. This code provides the following behaviors:
Allows the viewmodel to mark itself as having served its purpose, causing the window to close.
Allows attached properties to be specified by individual views that can affect the way the window appears on-screen, e.g. the window title.
Can be extended to notify presented items that the user has tried closing the window, allowing interception/cancellation or cleanup actions to be performed.
Code:
public class PopupHost : Window
{
private readonly AwaitableViewModelBase _viewModel;
public PopupHost(Window owner, AwaitableViewModelBase viewModel, string dataTemplateKey = null)
{
Owner = owner;
_viewModel = viewModel;
// Wrap the content in another presenter -- makes it a little easier to get to in order to look for attached properties.
var contentPresenter = new ContentPresenter
{
Content = viewModel
};
if (!string.IsNullOrWhiteSpace(dataTemplateKey))
contentPresenter.ContentTemplate = (DataTemplate) FindResource(dataTemplateKey);
Content = contentPresenter;
Task.Run(async () =>
{
await viewModel.Task;
Dispatcher.Invoke(Close);
});
Closed += ClosedHandler;
ApplyTemplate();
// Grab attached property values from the user control (or whatever element... you just need to find the descendant)
var contentElement = FindDescendantWithNonDefaultPropertyValue(contentPresenter, PopupWindowProperties.TitleProperty);
if (contentElement != null)
{
var binding = new Binding { Source = contentElement, Path = new PropertyPath(PopupWindowProperties.TitleProperty) };
SetBinding(TitleProperty, binding);
}
}
private void ClosedHandler(object sender, EventArgs args)
{
_viewModel?.Cancel();
Closed -= ClosedHandler;
}
private static Visual FindDescendant(Visual element, Predicate<Visual> predicate)
{
if (element == null)
return null;
if (predicate(element))
return element;
Visual foundElement = null;
(element as FrameworkElement)?.ApplyTemplate();
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(element); i++)
{
var visual = VisualTreeHelper.GetChild(element, i) as Visual;
foundElement = FindDescendant(visual, predicate);
if (foundElement != null)
break;
}
return foundElement;
}
private static Visual FindDescendantWithNonDefaultPropertyValue(Visual element, DependencyProperty dp)
{
return FindDescendant(element, e => !(dp.GetMetadata(e).DefaultValue ?? new object()).Equals(e.GetValue(dp)));
}
}
PopupWindowProperties
Just a dumb object containing solely attached properties so your views can convey some information to the window.
public static class PopupWindowProperties
{
public static readonly DependencyProperty TitleProperty = DependencyProperty.RegisterAttached("Title", typeof(string), typeof(PopupWindowProperties), new FrameworkPropertyMetadata(string.Empty));
public static void SetTitle(UIElement element, string value) => element.SetValue(TitleProperty, value);
public static string GetTitle(UIElement element) => element.GetValue(TitleProperty) as string;
}
AwaitableViewModelBase
A simple abstract viewmodel which has a TaskCompletionSource. This allows the popup window and the viewmodel to coordinate closing.
public abstract class AwaitableViewModelBase : ViewModelBase
{
protected TaskCompletionSource<bool> TaskCompletionSource { get; set; }
public Task<bool> Task => TaskCompletionSource?.Task;
public void RegisterTaskCompletionSource(TaskCompletionSource<bool> tcs)
{
var current = TaskCompletionSource;
if (current != null && current.Task.Status == TaskStatus.Running)
throw new InvalidOperationException();
TaskCompletionSource = tcs;
}
public virtual void Cancel() => SetResult(false);
protected void SetResult(bool result) => TaskCompletionSource?.TrySetResult(result);
}
WindowService
Last but not least, the simple service that can present the requested view and viewmodel. You can use implicit DataTemplates for your viewmodels, or provide the specific x:Key value of the template you wish to use. Note that the await doesn't really do anything here because ShowDialog blocks. We return the bool since it can be used to easily identify if the user hit OK or Cancel on a modal.
public class WindowService
{
public async Task<bool> ShowModalAsync(AwaitableViewModelBase viewModel, string dataTemplateKey = null)
{
var tcs = new TaskCompletionSource<bool>();
viewModel.RegisterTaskCompletionSource(tcs);
Application.Current.Dispatcher.Invoke(() =>
{
var currentWindow = Application.Current.Windows.OfType<Window>().SingleOrDefault(x => x.IsActive) ?? Application.Current.MainWindow;
var window = new PopupHost(currentWindow, viewModel, dataTemplateKey);
window.ShowDialog();
});
return await viewModel.Task;
}
}

Horizontal aligment WPF expander header

I want to show my GroupName on left and button "ShowOnly" on the right of header row.
I tried with this code but doesn't works.
Could anyone help me?
Thx
My code :
<Expander IsExpanded="True" >
<Expander.Header>
<DockPanel HorizontalAlignment="Stretch">
<TextBlock Text="{Binding Path=Name}" FontSize="18"></TextBlock>
<Button Style="{StaticResource ButtonStyle}" Content="Show Only" HorizontalAlignment="Right" Padding="15,0,15,0" Click="Button_Click"></Button>
</DockPanel>
</Expander.Header>
<Expander.Style>
<Style TargetType="{x:Type Expander}">
<Setter Property="Background" Value="#f0f0f5"></Setter>
<Setter Property="TextElement.FontFamily" Value="Arial Nova"/>
</Style>
</Expander.Style>
<Expander.Content>
<ItemsPresenter />
</Expander.Content>
</Expander>
My ButtonStyle :
<Style x:Key="ButtonStyle" TargetType="Button">
<Setter Property="Background" Value="#66e0ff" />
<Setter Property="Foreground" Value="White" />
<Setter Property="FontSize" Value="15" />
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border CornerRadius="4" Background="{TemplateBinding Background}">
<Grid>
<ContentPresenter x:Name="MyContentPresenter" Content="{TemplateBinding Content}" HorizontalAlignment="Center" VerticalAlignment="Center" />
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="White" />
<Setter Property="Foreground" Value="#66e0ff" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I tried also with an DockPanel, but same result.

You need to set the HorizontalAlignment property of the ContentPresenter that is defined in the Expander's default control template to Stretch.
The easiest way to do this is probably to handle the Loaded event of the Expander and use a helper method that finds the ContentPresenter in the visual tree:
private void Expander_Loaded(object sender, RoutedEventArgs e)
{
Expander expander = sender as Expander;
System.Windows.Controls.Primitives.ToggleButton HeaderSite = GetChildOfType<System.Windows.Controls.Primitives.ToggleButton>(expander);
if (HeaderSite != null)
{
ContentPresenter cp = GetChildOfType<ContentPresenter>(HeaderSite);
if (cp != null)
cp.HorizontalAlignment = HorizontalAlignment.Stretch;
}
}
private static T GetChildOfType<T>(DependencyObject depObj) where T : DependencyObject
{
if (depObj == null) return null;
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
{
var child = VisualTreeHelper.GetChild(depObj, i);
var result = (child as T) ?? GetChildOfType<T>(child);
if (result != null) return result;
}
return null;
}
<Expander IsExpanded="True" Loaded="Expander_Loaded">
<Expander.Header>
<DockPanel HorizontalAlignment="Stretch">
<Button Style="{StaticResource ButtonStyle}" Content="Show Only" DockPanel.Dock="Right" Padding="15,0,15,0" Click="Button_Click"></Button>
<TextBlock Text="{Binding Path=Name}" FontSize="18"></TextBlock>
</DockPanel>
</Expander.Header>
<Expander.Style>
<Style TargetType="{x:Type Expander}">
<Setter Property="Background" Value="#f0f0f5"></Setter>
<Setter Property="TextElement.FontFamily" Value="Arial Nova"/>
</Style>
</Expander.Style>
<Expander.Content>
<ItemsPresenter />
</Expander.Content>
</Expander>

Set width of DockPanel to width of expander so that it will stretch properly.
<DockPanel HorizontalAlignment="Stretch" Width="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Expander}}, Path=ActualWidth}">

You can refer to these solutions:
https://joshsmithonwpf.wordpress.com/2007/02/24/stretching-content-in-an-expander-header/

Click Event Not Firing After Changing ObservableCollection

I am not experienced with WPF, so please forgive my lack of understanding.
EDIT: I'm working on a simplistic chess GUI, and the pieces move fine until one tries to move a piece that has already been moved. If we try to move the piece to a previously occupied square, the click event won't fire at all. If we try to move it to a previously untouched square, the event will fire, but the UI won't update.
Here's the XAML for the chessboard (borrowed from here: WPF controls needed to build chess application):
<Window x:Class="Client.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:Client"
xmlns:defaults="clr-namespace:butnotquite.Defaults;assembly=butnotquite"
mc:Ignorable="d"
Title="butnotquite Chess" Height="600" Width="600">
<Window.Resources>
<DrawingBrush x:Key="Checkerboard" Stretch="None" TileMode="Tile" Viewport="0,0,2,2" ViewportUnits="Absolute">
<DrawingBrush.Drawing>
<DrawingGroup>
<GeometryDrawing Brush="Tan">
<GeometryDrawing.Geometry>
<RectangleGeometry Rect="0,0,2,2" />
</GeometryDrawing.Geometry>
</GeometryDrawing>
<GeometryDrawing Brush="Brown">
<GeometryDrawing.Geometry>
<GeometryGroup>
<RectangleGeometry Rect="0,0,1,1" />
<RectangleGeometry Rect="1,1,1,1" />
</GeometryGroup>
</GeometryDrawing.Geometry>
</GeometryDrawing>
</DrawingGroup>
</DrawingBrush.Drawing>
</DrawingBrush>
<Style x:Key="PieceStyle" TargetType="{x:Type Image}">
<Style.Triggers>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding PieceType}" Value="{x:Static defaults:PieceType.None}"/>
<Condition Binding="{Binding Color}" Value="{x:Static defaults:Color.None}"/>
</MultiDataTrigger.Conditions>
<MultiDataTrigger.Setters>
<Setter Property="Image.Source" Value="/Images/empty_square.png" />
</MultiDataTrigger.Setters>
</MultiDataTrigger>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding PieceType}" Value="{x:Static defaults:PieceType.Pawn}"/>
<Condition Binding="{Binding Color}" Value="{x:Static defaults:Color.White}"/>
</MultiDataTrigger.Conditions>
<MultiDataTrigger.Setters>
<Setter Property="Image.Source" Value="/Images/white_pawn.png" />
</MultiDataTrigger.Setters>
</MultiDataTrigger>
</Style.Triggers>
</Style>
</Window.Resources>
<Viewbox>
<ItemsControl Name="ChessboardUI">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<Canvas Width="8" Height="8" Background="{StaticResource Checkerboard}"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Name="square" PreviewMouseDown="square_MouseLeftButtonDown" Width="1" Height="1" >
<Image Width="0.8" Height="0.8" Style="{StaticResource PieceStyle}"/>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemContainerStyle>
<Style>
<Setter Property="Canvas.Left" Value="{Binding Position.X}" />
<Setter Property="Canvas.Top" Value="{Binding Position.Y}" />
</Style>
</ItemsControl.ItemContainerStyle>
</ItemsControl>
</Viewbox>
</Window>
I've ommitted the multidata triggers for all pieces as they are all similar.
Here's the viewmodel. I'm using the MVVMLight library:
public class PieceViewModel : ViewModelBase
{
private PieceType pieceType;
private Color color;
private Point position;
public PieceType PieceType
{
get
{
return this.pieceType;
}
set
{
this.pieceType = value;
base.RaisePropertyChanged(() => this.PieceType);
}
}
public Color Color
{
get
{
return this.color;
}
set
{
this.color = value;
base.RaisePropertyChanged(() => this.Color);
}
}
public Point Position
{
get
{
return this.position;
}
set
{
this.position = value;
base.RaisePropertyChanged(() => this.Position);
}
}
}
Here's how I fill the ObservableCollection:
private void BindPieces()
{
this.chessboard = new Chessboard(false);
this.pieces = new ObservableCollection<PieceViewModel>();
for (int square = 0; square < this.chessboard.Board.Length; square++)
{
int x = square % 8;
int y = square / 8;
Point position = new Point(x, y);
PieceViewModel pieceModel = new PieceViewModel()
{
PieceType = this.chessboard.Board[square].OccupiedBy.Type,
Color = this.chessboard.Board[square].OccupiedBy.Color,
Position = position
};
this.pieces.Add(pieceModel);
}
this.ChessboardUI.ItemsSource = this.pieces;
}
More code can be found here: https://github.com/YouJinTou/butnotquite/tree/master/Client
Thanks for any and all help.

As lokusking has commented, the collection needs to be instantiated only once, which was the case here; however, I had failed to clear it and rebind it after every click. It seems like a hackish solution, but it works.