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Binding to ItemsSource and SelectedItem of a ComboBox with custom Style (WPF .NET Core MVVM)

I am trying to bind the ItemsSource and SelectedItem properties of a ComboBox and the items are not displaying properly. The ComboBox is populated with the values of an Enum based on a solution suggested in this post. I have defined the ComboBox on the View as follows:
<ComboBox
Grid.Column="1"
Grid.Row="2"
ItemContainerStyle="{DynamicResource ComboBoxItemStyle}"
Style="{DynamicResource MaterialComboBox}"
SelectedItem="{Binding SelectedSetting}" ItemsSource="{Binding SettingOptions}" />
The properties on ViewModel I bind to are defined as follows:
private DataUpdateRate _selectedSetting;
public DataUpdateRate SelectedSetting
{
get { return _selectedSetting; }
set
{
_selectedSetting = value;
OnPropertyChanged("SelectedMyEnumType");
}
}
public IEnumerable<DataUpdateRate> SettingOptions
{
get
{
return Enum.GetValues(typeof(DataUpdateRate))
.Cast<DataUpdateRate>();
}
}
To the same ComboBox, I have also applied a custom style and template. My guess is that the issue lies in the DataTemplate I defined for the ContentPresenter
<!-- ItemTemplate-->
<Style x:Key="ComboBoxItemStyle" TargetType="{x:Type ComboBoxItem}">
<Setter Property="SnapsToDevicePixels" Value="True"/>
<Setter Property="Padding" Value="6 4"/>
<Setter Property="HorizontalContentAlignment" Value="{Binding HorizontalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment, RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}}"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ComboBoxItem}">
<Border
x:Name="itemBorder"
Background="{TemplateBinding Background}"
Padding="{TemplateBinding Padding}"
SnapsToDevicePixels="true">
<TextBlock
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
Text="{TemplateBinding Content}"
FontSize="16"
FontWeight="Medium"/>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" TargetName="itemBorder" Value="{StaticResource SurfaceElevation5Brush}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<!-- Toggle Button (main button with arrow) -->
<Style x:Key="ComboBoxToggleButton" TargetType="{x:Type ToggleButton}">
<Setter Property="OverridesDefaultStyle" Value="true"/>
<Setter Property="IsTabStop" Value="false"/>
<Setter Property="Focusable" Value="false"/>
<Setter Property="ClickMode" Value="Press"/>
<Setter Property="Height" Value="40" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border
x:Name="templateRoot"
Background="{StaticResource SurfaceElevation2Brush}"
BorderBrush="{StaticResource SurfaceElevation5Brush}"
BorderThickness="0 0 0 1.5"
CornerRadius="5 5 0 0"
SnapsToDevicePixels="true">
<Border
SnapsToDevicePixels="true"
HorizontalAlignment="Right"
VerticalAlignment="Center"
Margin="6 0">
<Viewbox Width="15" Height="15">
<Path
x:Name="arrow"
Stretch="Fill"
Data="M24 30 14 20.05H34Z"
Fill="{StaticResource SurfaceElevation5Brush}"/>
</Viewbox>
</Border>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="BorderBrush" TargetName="templateRoot" Value="{StaticResource PrimaryLightBrush}" />
<Setter Property="Fill" TargetName="arrow" Value="{StaticResource PrimaryLightBrush}"/>
</Trigger>
<MultiDataTrigger>
<MultiDataTrigger.Conditions>
<Condition Binding="{Binding IsChecked, RelativeSource={RelativeSource Self}}" Value="True"/>
</MultiDataTrigger.Conditions>
<Setter Property="BorderBrush" TargetName="templateRoot" Value="{StaticResource PrimaryBrush}" />
<Setter Property="Fill" TargetName="arrow" Value="{StaticResource PrimaryBrush}"/>
</MultiDataTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<ControlTemplate x:Key="ComboBoxTemplate" TargetType="{x:Type ComboBox}">
<Grid SnapsToDevicePixels="True">
<!-- Popup -->
<Popup
x:Name="PART_Popup"
AllowsTransparency="true"
IsOpen="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
Placement="Bottom"
PopupAnimation="Slide">
<!-- This is the actual dropdown part-->
<Border
x:Name="dropDownBorder"
SnapsToDevicePixels="True"
MinWidth="{TemplateBinding FrameworkElement.ActualWidth}"
MaxHeight="{TemplateBinding ComboBox.MaxDropDownHeight}"
Background="{StaticResource SurfaceElevation3Brush}"
CornerRadius="0 0 5 5">
<ScrollViewer x:Name="DropDownScrollViewer">
<ItemsPresenter
x:Name="ItemsPresenter"
KeyboardNavigation.DirectionalNavigation="Contained"
SnapsToDevicePixels="True"
/>
</ScrollViewer>
</Border>
</Popup>
<!-- ToggleButton -->
<ToggleButton
x:Name="toggleButton"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
Style="{StaticResource ComboBoxToggleButton}"/>
<!-- ContentPresenter -->
<ContentPresenter
x:Name="contentPresenter"
ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}"
Content="{TemplateBinding SelectionBoxItem}"
ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
IsHitTestVisible="false"
Margin="10 0"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
<ContentPresenter.ContentTemplate>
<DataTemplate>
<TextBlock Text="{TemplateBinding Content}" FontSize="16"/>
</DataTemplate>
</ContentPresenter.ContentTemplate>
</ContentPresenter>
</Grid>
</ControlTemplate>
<!-- Main ComboBo Style -->
<Style x:Key="MaterialComboBox" TargetType="{x:Type ComboBox}">
<Setter Property="Foreground" Value="{StaticResource ForegroundLightBrush}"/>
<Setter Property="Padding" Value="6,3,5,3"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="Margin" Value="20 0" />
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
<Setter Property="ScrollViewer.CanContentScroll" Value="true"/>
<Setter Property="ScrollViewer.PanningMode" Value="Both"/>
<Setter Property="VerticalContentAlignment" Value="Center" />
<Setter Property="Template" Value="{StaticResource ComboBoxTemplate}"/>
</Style>
When I run the application the ComboBox expands according to the number of elements in the Enum, suggesting that it does generate the ComboBoxItems correctly, but doesn't display the values of the items. I have also tried another solution from the post I referenced earlier with the same result.
I assume that I have done something wrong with the ComboBox template, but I can't put my finger on it. If anyone has a solution I would greatly appreciate it.

How to give Expander Full Width of Column in a Grid

I have an Expander and it should receive the full width of the column but I cant get it to work.
I tried to add the Horizontal(Content)Alignment = stretch on the TextBlock and on the Expander itself even on the Grid, but it is not working.
What I need is that the Expander takes about 90% of the width and the rest are assigned to the buttons as in the following example:
I want to display e.g. a name and when you press on it, expands down and shows additional information
and if the buttons are pressed, then the commands behind the buttons will be executed (no commands are binded in the example).
<ListView
ItemsSource="{Binding log}"
SelectionMode="Multiple"
Style="{StaticResource ListViewStyle}">
<ListView.ItemTemplate>
<DataTemplate>
<Border BorderThickness="0,0,0,1" BorderBrush="Gray">
<Grid HorizontalAlignment="Stretch">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100*" />
<ColumnDefinition Width="5*" />
<ColumnDefinition Width="5*" />
</Grid.ColumnDefinitions>
<Expander Grid.Column="0"
HorizontalAlignment="Stretch"
IsExpanded="{Binding Mode=TwoWay, Path=IsSelected, RelativeSource={RelativeSource AncestorType=ListBoxItem, Mode=FindAncestor}}"
Style="{StaticResource ExpanderStyle}">
<Expander.Header>
<TextBlock Text="{Binding Name}" Foreground="White"
HorizontalAlignment="Stretch" />
</Expander.Header>
<TextBlock
VerticalAlignment="Center"
FontSize="16"
Foreground="White"
Text="{Binding Description}" />
</Expander>
<Button Grid.Column="1"
Style="{StaticResource IconButton}">
<Button.Background>
<ImageBrush ImageSource="../icons/edit.png"
Stretch="None" />
</Button.Background>
</Button>
<dialogButton:ConfirmButton Grid.Column="2"
Question="{x:Static language:Strings.confirm}"
Style="{DynamicResource IconButton}"
Margin="0,0,10,0">
<dialogButton:ConfirmButton.Background>
<ImageBrush ImageSource="../icons/delete.png"
Stretch="None" />
</dialogButton:ConfirmButton.Background>
</dialogButton:ConfirmButton>
</Grid>
</Border>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
Styles
<Style x:Key="ExpanderDownHeaderStyle" TargetType="{x:Type ToggleButton}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Border Padding="{TemplateBinding Padding}">
<Grid Background="Transparent" SnapsToDevicePixels="False">
<ContentPresenter HorizontalAlignment="Stretch" Margin="0" RecognizesAccessKey="True" SnapsToDevicePixels="True" VerticalAlignment="Center"/>
</Grid>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="ExpanderStyle" TargetType="{x:Type Expander}">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="Background" Value="Transparent"/>
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Stretch"/>
<Setter Property="BorderBrush" Value="Transparent"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Expander}">
<Border Background="{TemplateBinding Background}" BorderThickness="{TemplateBinding BorderThickness}" BorderBrush="{TemplateBinding BorderBrush}" CornerRadius="3" SnapsToDevicePixels="true">
<DockPanel>
<ToggleButton x:Name="HeaderSite" ContentTemplate="{TemplateBinding HeaderTemplate}" Content="{TemplateBinding Header}" ContentTemplateSelector="{TemplateBinding HeaderTemplateSelector}" DockPanel.Dock="Top" FontStyle="{TemplateBinding FontStyle}" FontStretch="{TemplateBinding FontStretch}" FontWeight="{TemplateBinding FontWeight}" FocusVisualStyle="{StaticResource ExpanderHeaderFocusVisual}" FontFamily="{TemplateBinding FontFamily}" Foreground="{TemplateBinding Foreground}" FontSize="{TemplateBinding FontSize}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" IsChecked="{Binding IsExpanded, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}" MinHeight="0" MinWidth="0" Margin="1" Padding="{TemplateBinding Padding}" Style="{StaticResource ExpanderDownHeaderStyle}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"/>
<ContentPresenter x:Name="ExpandSite" DockPanel.Dock="Bottom" Focusable="false" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" Visibility="Collapsed"/>
</DockPanel>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsExpanded" Value="true">
<Setter Property="Visibility" TargetName="ExpandSite" Value="Visible"/>
</Trigger>
<Trigger Property="ExpandDirection" Value="Down">
<Setter Property="DockPanel.Dock" TargetName="ExpandSite" Value="Bottom"/>
<Setter Property="DockPanel.Dock" TargetName="HeaderSite" Value="Top"/>
<Setter Property="Background" Value="Transparent" />
<Setter Property="Style" TargetName="HeaderSite" Value="{StaticResource ExpanderDownHeaderStyle}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
I also tried things from the following Threads
wpf - Header of Expander fit contents width?
Problem here is that the Buttons are pushed out of the view
Best Solution would be if the Expander just takes the width of the column so that I can adjust the widths of the element by the Grid.ColumnDefinition.

The issue is that the item container, a ListViewItem does not stretch its content by default. You have to create an item container style in order to set the HorizontalContentAlignment to Stretch.
<ListView.ItemContainerStyle>
<Style TargetType="{x:Type ListViewItem}">
<Setter Property="HorizontalContentAlignment" Value="Stretch"/>
</Style>
</ListView.ItemContainerStyle>

XAML, move two contentcontrol inside a button with animation

Is it possible to move two contentcontrol inside a button and also resize this said button?
<Button Height="100" Width="100">
<Grid>
<Grid.RowDefinitions>
<RowDefinition height="30"/>
<RowDefinition height="30"/>
</Grid.RowDefinitions>
<Image Grid.Row="0" Source="img.jpg"/>
<TextBlock Grid.Row="1" Text="Some content"/>
</Grid>
</Button>
I would like to align them horizontally instead of vertically on MouseOver and resize the button from 100 to 50, is this possible ?

This can be achieved with a style:
<Style x:Key="ExampleButtonStyle" TargetType="{x:Type Button}">
<Setter Property="Background" Value="LightGray"/>
<Setter Property="BorderBrush" Value="Black"/>
<Setter Property="Foreground" Value="Black"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Padding" Value="1"/>
<Setter Property="Height" Value="100"/>
<Setter Property="Width" Value="100"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
<UniformGrid x:Name="uGrid">
<Image Source="img.jpg" />
<ContentPresenter x:Name="contentPresenter" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</UniformGrid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="false">
<Setter TargetName="uGrid" Property="Rows" Value="2" />
<Setter TargetName="uGrid" Property="Columns" Value="1" />
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter TargetName="uGrid" Property="Columns" Value="2" />
<Setter TargetName="uGrid" Property="Rows" Value="1" />
<Setter Property="Height" Value="50" />
<Setter Property="Width" Value="50" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
This style defines a modified template for your button, and can leverage triggers to respond to mouse events.
To add the style to your button, do the following:
<Grid>
<Grid.Resources>
<!-- Put Style Here -->
</Grid.Resources>
<Button Style="{DynamicResource ExampleButtonStyle}">
<TextBlock Grid.Row="1" Text="Some content"/>
</Button>
</Grid>
How you distribute your code between the style and the control instance is up to you. You will likely want to keep things modular and reusable.
Anatomy of a Style
If you haven't explored styles before, they can be a bit daunting and verbose. I have explained the components of the provided style below.
You would start a new style by declaring the Style. Here you must nominate a target type (what you want to apply the style to) and a Key (the name of the style resource:
<Style x:Key="ExampleButtonStyle" TargetType="{x:Type Button}">
<!-- Style content goes here. -->
</Style>
Setters are used to make the style apply values to properties of the target control. For example:
<Setter Property="Background" Value="LightGray"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Height" Value="100"/>
<Setter Property="Width" Value="100"/>
Because you want to change the layout of the button, you will want to nominate a control template. To do this, use a Setter to set the Template property of the button. The template here can include any layout you want. The ContentPresenter is used to display the body of the Button tag from your implementation:
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
<UniformGrid x:Name="uGrid">
<Image Source="img.jpg" />
<ContentPresenter x:Name="contentPresenter" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</UniformGrid>
</Border>
<ControlTemplate.Triggers>
<!-- Triggers here -->
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
Finally, you need to add triggers to make the control template update with interaction. The trigger essentially observes a property of the control, and applies when its value matches the value nominated by the trigger. This updates the control using the setters within.
<Trigger Property="IsMouseOver" Value="false">
<Setter TargetName="uGrid" Property="Rows" Value="2" />
<Setter TargetName="uGrid" Property="Columns" Value="1" />
</Trigger>
Layout
To achieve your layout goal I used a UniformGrid. The UniformGrid divides itself into equal cells to match the number of content items within. Note that this is available in WPF, but not UWP. On the UniformGrid, you can set a Columns or Rows count, and the grid will compensate as necessary. In the style above, I am changing the nominated Row and Column counts and letting the grid adjust itself layout accordingly. This visually swaps content from rows to columns.
Concerns
There are other methods that could achieve this more elegantly, but Styles offer a large amount of flexibility, and have a smaller learning curve.
You stated that you wanted to change the button size from 100 to 50 (I am assuming on both axis?) and I must advise you against this. You will see what happens when you apply the provided style; the button starts as a 100x100 square. A user moves the mouse over the button to just inside the button's edge. The button rapidly changes from 50x50 to 100x100 until the mouse is moved to the centre or off the button entirely. This offers a poor and confusing user experience, and deserves some more thought.

this might be late, but according to what have been said in the comments, this could do the trick, i have worked on something similar recently
<Style x:Key="btnSubMenu" TargetType="{x:Type Button}">
<Setter Property="Background" Value="White"/>
<Setter Property="BorderBrush" Value="Black"/>
<Setter Property="Foreground" Value="Black"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="HorizontalAlignment" Value="Stretch"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="VerticalAlignment" Value="Stretch"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Padding" Value="1"/>
<Setter Property="FontFamily" Value="Segoe UI"/>
<Setter Property="FontSize" Value="20"/>
<Setter Property="FontWeight" Value="ExtraBold"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Button}">
<Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="true">
<Grid x:Name="uGrid2">
<Grid.RowDefinitions>
<RowDefinition Height="*"/>
<RowDefinition Height="2*"/>
<RowDefinition Height="auto"/>
</Grid.RowDefinitions>
<Image Grid.Row="0" Source="/Images/1.png" />
<ContentPresenter x:Name="contentPresenter" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
<Grid Grid.Row="2" Name="Gbexample" Visibility="Collapsed">
<Grid.RowDefinitions>
<RowDefinition Height="40"/>
<RowDefinition Height="40"/>
<RowDefinition Height="40"/>
<RowDefinition Height="40"/>
</Grid.RowDefinitions>
<Button Grid.Row="0" Style="{DynamicResource btnSubSubMenu}" Content="{DynamicResource strCity}" Name="btnCity"/>
<Button Grid.Row="1" Style="{DynamicResource btnSubSubMenu}" Content="{DynamicResource strCountry}" Name="btnCountry"/>
<Button Grid.Row="2" Style="{DynamicResource btnSubSubMenu}" Content="{DynamicResource strStore}" Name="btnStoreIn"/>
<Button Grid.Row="3" Style="{DynamicResource btnSubSubMenu}" Content="{DynamicResource strLocation}" Name="btnLocation"/>
</Grid>
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="false">
<Setter TargetName="Gbproduct" Property="Visibility" Value="Collapsed" />
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter TargetName="Gbproduct" Property="Visibility" Value="Visible" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

WPF CheckComboBox styling with MahApps.Metro

How can I style WPF Extended Toolkit's CheckComboBox with MahApps.Metro?
My App.xaml contains:
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colors.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Blue.xaml" />
<ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseLight.xaml" />
When I put CheckComboBox on Window it looks like this:
And simple ComboBox looks like this:
So the styles are different.

I created simple MahApps.Metro custom style based on latest WPF Extended Toolkit's CheckComboBox style. It's maybe not perfect but works for me™.
Result:
Here are the style simply in the resources tag of the main window:
<Window.Resources>
<xctk:InverseBoolConverter x:Key="InverseBoolConverter" />
<Style BasedOn="{StaticResource {x:Type xctk:SelectorItem}}" TargetType="{x:Type xctk:SelectorItem}">
<Setter Property="Foreground" Value="{DynamicResource TextBrush}" />
<Setter Property="Padding" Value="2" />
<Setter Property="RenderOptions.ClearTypeHint" Value="Enabled" />
<Setter Property="Background" Value="{DynamicResource WhiteBrush}" />
<Setter Property="BorderThickness" Value="0" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type xctk:SelectorItem}">
<Grid Margin="0,0.5" Background="{TemplateBinding Background}">
<Border x:Name="_background"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
<CheckBox Margin="0.5,0"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
Content="{TemplateBinding Content}"
ContentTemplate="{TemplateBinding ContentTemplate}"
ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
Foreground="{TemplateBinding Foreground}"
IsChecked="{Binding IsSelected, RelativeSource={RelativeSource TemplatedParent}}"
Padding="{TemplateBinding Padding}" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected" Value="true">
<Setter TargetName="_background" Property="Background" Value="{DynamicResource AccentColorBrush}" />
<Setter Property="Foreground" Value="{DynamicResource AccentSelectedColorBrush}" />
</Trigger>
<Trigger Property="IsMouseOver" Value="true">
<Setter TargetName="_background" Property="Background" Value="{DynamicResource AccentColorBrush2}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="CheckComboBoxToggleButton" TargetType="{x:Type ToggleButton}">
<Setter Property="OverridesDefaultStyle" Value="true" />
<Setter Property="IsTabStop" Value="false" />
<Setter Property="Focusable" Value="false" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ToggleButton}">
<Grid>
<Border x:Name="Background"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
<Grid Margin="1">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="0" MinWidth="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Grid}}, Path=ActualHeight, Mode=OneWay}" />
</Grid.ColumnDefinitions>
<TextBox Margin="1"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
Background="Transparent"
BorderThickness="0"
Cursor="Arrow"
Focusable="False"
HorizontalScrollBarVisibility="Hidden"
IsReadOnly="True"
Padding="{TemplateBinding Padding}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
Text="{TemplateBinding Content}"
VerticalScrollBarVisibility="Hidden" />
<Grid x:Name="ArrowBackground"
Grid.Column="1"
Background="Transparent">
<Path x:Name="Arrow"
Width="8"
Height="4"
HorizontalAlignment="Center"
VerticalAlignment="Center"
Data="F1 M 301.14,-189.041L 311.57,-189.041L 306.355,-182.942L 301.14,-189.041 Z "
Fill="{DynamicResource GrayBrush1}"
IsHitTestVisible="false"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
Stretch="Uniform" />
</Grid>
</Grid>
</Grid>
<ControlTemplate.Triggers>
<Trigger SourceName="ArrowBackground" Property="IsMouseOver" Value="True">
<Setter TargetName="ArrowBackground" Property="Background" Value="{DynamicResource GrayBrush5}" />
</Trigger>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="Background" Property="Background" Value="{DynamicResource GrayBrush8}" />
</Trigger>
<Trigger Property="IsPressed" Value="True">
<Setter TargetName="Background" Property="Background" Value="{DynamicResource GrayBrush7}" />
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter TargetName="Arrow" Property="Fill" Value="#AFAFAF" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style BasedOn="{StaticResource {x:Type xctk:CheckComboBox}}" TargetType="{x:Type xctk:CheckComboBox}">
<Setter Property="MinHeight" Value="26" />
<Setter Property="Foreground" Value="{DynamicResource TextBrush}" />
<Setter Property="Background" Value="{DynamicResource ControlBackgroundBrush}" />
<Setter Property="BorderBrush" Value="{DynamicResource TextBoxBorderBrush}" />
<Setter Property="BorderThickness" Value="1" />
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto" />
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
<Setter Property="Padding" Value="1" />
<Setter Property="ScrollViewer.PanningMode" Value="Both" />
<Setter Property="Stylus.IsFlicksEnabled" Value="False" />
<Setter Property="VerticalContentAlignment" Value="Center" />
<Setter Property="HorizontalContentAlignment" Value="Stretch" />
<Setter Property="FontFamily" Value="{DynamicResource ContentFontFamily}" />
<Setter Property="FontSize" Value="{DynamicResource ContentFontSize}" />
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="Validation.ErrorTemplate" Value="{DynamicResource ValidationErrorTemplate}" />
<Setter Property="ScrollViewer.CanContentScroll" Value="False" />
<Setter Property="Controls:ControlsHelper.FocusBorderBrush" Value="{DynamicResource ComboBoxMouseOverInnerBorderBrush}" />
<Setter Property="Controls:ControlsHelper.MouseOverBorderBrush" Value="{DynamicResource TextBoxMouseOverBorderBrush}" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type xctk:CheckComboBox}">
<Grid x:Name="MainGrid" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}">
<Popup x:Name="PART_Popup"
AllowsTransparency="true"
Focusable="False"
IsOpen="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
Placement="Bottom"
PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}"
StaysOpen="False">
<Grid MinWidth="{Binding ActualWidth, ElementName=MainGrid}" MaxHeight="{Binding MaxDropDownHeight, RelativeSource={RelativeSource TemplatedParent}}">
<Border x:Name="DropDownBorder"
Height="Auto"
Background="{DynamicResource WhiteBrush}"
BorderBrush="{DynamicResource ComboBoxPopupBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
Effect="{DynamicResource DropShadowBrush}" />
<ScrollViewer x:Name="DropDownScrollViewer"
BorderThickness="0"
Padding="1">
<ItemsPresenter x:Name="PART_ItemsPresenter"
KeyboardNavigation.DirectionalNavigation="Contained"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
</ScrollViewer>
</Grid>
</Popup>
<Border Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
<ToggleButton x:Name="PART_DropDownButton"
Margin="0"
VerticalAlignment="Stretch"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
Content="{TemplateBinding Text}"
Focusable="False"
Foreground="{TemplateBinding Foreground}"
IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}"
IsHitTestVisible="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource InverseBoolConverter}}"
Padding="{TemplateBinding Padding}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
Style="{DynamicResource CheckComboBoxToggleButton}" />
<Border x:Name="FocusBorder"
Background="{x:Null}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
Visibility="Collapsed" />
<Border x:Name="DisabledVisualElement"
Background="{DynamicResource ControlsDisabledBrush}"
BorderBrush="{DynamicResource ControlsDisabledBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
IsHitTestVisible="False"
Opacity="0.6"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
Visibility="Collapsed" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="FocusBorder" Property="Visibility" Value="Visible" />
<Setter TargetName="FocusBorder" Property="BorderBrush" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(Controls:ControlsHelper.MouseOverBorderBrush)}" />
</Trigger>
<Trigger Property="IsFocused" Value="True">
<Setter TargetName="FocusBorder" Property="Visibility" Value="Visible" />
<Setter TargetName="FocusBorder" Property="BorderBrush" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(Controls:ControlsHelper.FocusBorderBrush)}" />
</Trigger>
<Trigger Property="IsKeyboardFocusWithin" Value="True">
<Setter TargetName="FocusBorder" Property="Visibility" Value="Visible" />
<Setter TargetName="FocusBorder" Property="BorderBrush" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(Controls:ControlsHelper.FocusBorderBrush)}" />
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter TargetName="DisabledVisualElement" Property="Visibility" Value="Visible" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>

Just adding to excellent punker's answer
Punkers answer is missing DisplayMemberPath property, but do not fear! :)
Just add <ContentPresenter /> inside CheckBox (and throw out TemplateBinding.Content which is ignoring DisplayMemberPath):
(...)
<Style BasedOn="{StaticResource {x:Type xctk:SelectorItem}}" TargetType="{x:Type xctk:SelectorItem}">
(...)
<Setter Property="Template">
<ControlTemplate>
(...)
<CheckBox Margin="0.5,0"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
ContentTemplate="{TemplateBinding ContentTemplate}"
ContentTemplateSelector="{TemplateBinding ContentTemplateSelector}"
Foreground="{TemplateBinding Foreground}"
IsChecked="{Binding IsSelected, RelativeSource={RelativeSource TemplatedParent}}"
Padding="{TemplateBinding Padding}">
<ContentPresenter />
</CheckBox>
(...)
</ControlTemplate>
</Style>
(...)

WPF replace checkmark from original checkbox

I'm trying to replace the checkmark of the standard WPF checkbox by my own checkmark (actually a Path). The checkbox should look like the standard one.
Where can I find the Microsoft xaml template of the checkbox, so I could modify it in the xaml? Or is there an more elegant way of doing this?
Note: I found already a template on MSDN ( http://msdn.microsoft.com/en-us/library/ms752319%28v=vs.110%29.aspx ), but it looks completely different.
Regards,
BlackTuareg

Step1 : Please Open New Project and Write Down Checkbox tag.
<Window x:Class="WpfApplication8.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:sys="clr-namespace:System;assembly=mscorlib"
Title="Window1" Height="300" Width="300">
<CheckBox Height="30" Width="200" Content="CheckBoxContent"></CheckBox>
</Window>
Designer View will look
Step 2: In Designer view ----Right click on CheckBox ->Edit Template->Edit A Copy
Step 3: Give name to style ->select resource window/checkobx ->ok
and Finally you can change/replace path by changing path in x:Name="markGrid"
<Style x:Key="CheckBoxStyle1" TargetType="{x:Type CheckBox}">
---------------------------
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type CheckBox}">
<Grid x:Name="templateRoot" Background="Transparent" SnapsToDevicePixels="True">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Border x:Name="checkBoxBorder" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
<!-- Change Path here-->
<Grid x:Name="markGrid">
<Path x:Name="optionMark" Data="F1M9.97498,1.22334L4.6983,9.09834 4.52164,9.09834 0,5.19331 1.27664,3.52165 4.255,6.08833 8.33331,1.52588E-05 9.97498,1.22334z" Fill="#FF212121" Margin="1" Opacity="0" Stretch="None"/>
<Rectangle x:Name="indeterminateMark" Fill="#FF212121" Margin="2" Opacity="0"/>
</Grid>
</Border>
<ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" Grid.Column="1" ContentStringFormat="{TemplateBinding ContentStringFormat}" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsChecked" Value="True">
-----------------------------------------
</Trigger>
<Trigger Property="IsChecked" Value="{x:Null}">
---------------------------------------
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Upadte :
<Window.Resources>
<Style TargetType="{x:Type CheckBox}">
<Setter Property="FocusVisualStyle">
<Setter.Value>
<Style>
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Margin="2" SnapsToDevicePixels="True" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Setter.Value>
</Setter>
<Setter Property="Background" Value="White"/>
<Setter Property="BorderBrush" Value="#FF707070"/>
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
<Setter Property="BorderThickness" Value="1"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type CheckBox}">
<Grid x:Name="templateRoot" Background="Transparent" SnapsToDevicePixels="True">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Border x:Name="checkBoxBorder" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
<Grid x:Name="markGrid">
<Path x:Name="optionMark" Data="F1M9.97498,1.22334L4.6983,9.09834 4.52164,9.09834 0,5.19331 1.27664,3.52165 4.255,6.08833 8.33331,1.52588E-05 9.97498,1.22334z" Fill="#FF212121" Margin="1" Opacity="0" Stretch="None"/>
<Rectangle x:Name="indeterminateMark" Fill="#FF212121" Margin="2" Opacity="0"/>
</Grid>
</Border>
<ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" Grid.Column="1" ContentStringFormat="{TemplateBinding ContentStringFormat}" Focusable="False" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="HasContent" Value="True">
<Setter Property="FocusVisualStyle">
<Setter.Value>
<Style>
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Margin="14,0,0,0" SnapsToDevicePixels="True" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2"/>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Setter.Value>
</Setter>
<Setter Property="Padding" Value="4,-1,0,0"/>
</Trigger>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" TargetName="checkBoxBorder" Value="#FFF3F9FF"/>
<Setter Property="BorderBrush" TargetName="checkBoxBorder" Value="#FF5593FF"/>
<Setter Property="Fill" TargetName="optionMark" Value="#FF212121"/>
<Setter Property="Fill" TargetName="indeterminateMark" Value="#FF212121"/>
</Trigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Background" TargetName="checkBoxBorder" Value="#FFE6E6E6"/>
<Setter Property="BorderBrush" TargetName="checkBoxBorder" Value="#FFBCBCBC"/>
<Setter Property="Fill" TargetName="optionMark" Value="#FF707070"/>
<Setter Property="Fill" TargetName="indeterminateMark" Value="#FF707070"/>
</Trigger>
<Trigger Property="IsPressed" Value="True">
<Setter Property="Background" TargetName="checkBoxBorder" Value="#FFD9ECFF"/>
<Setter Property="BorderBrush" TargetName="checkBoxBorder" Value="#FF3C77DD"/>
<Setter Property="Fill" TargetName="optionMark" Value="#FF212121"/>
<Setter Property="Fill" TargetName="indeterminateMark" Value="#FF212121"/>
</Trigger>
<Trigger Property="IsChecked" Value="True">
<Setter Property="Opacity" TargetName="optionMark" Value="1"/>
<Setter Property="Opacity" TargetName="indeterminateMark" Value="0"/>
</Trigger>
<Trigger Property="IsChecked" Value="{x:Null}">
<Setter Property="Opacity" TargetName="optionMark" Value="0"/>
<Setter Property="Opacity" TargetName="indeterminateMark" Value="1"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<Grid>
<CheckBox Height="40" Width="200" Content="ok"></CheckBox>
</Grid>

The linked template is simply some random template. It's not default CheckBox template.
You can easily extract templates yourself (see here for a full source, the page is in Russian, but code with English comments):
// get all control types
Type typeControl = typeof(Control);
List<Type> myTypes = new List<Type>();
Assembly assembly = Assembly.GetAssembly(typeof(Control));
foreach (Type type in assembly.GetTypes())
{
if (type.IsSubclassOf(typeControl) && !type.IsAbstract && type.IsPublic)
myTypes.Add(type);
}
Then for any specific type
// Instantiate the type.
ConstructorInfo info = type.GetConstructor(System.Type.EmptyTypes);
Control control = (Control)info.Invoke(null);
// Get the template.
ControlTemplate template = control.Template;
// Get the XAML for the template.
XmlWriterSettings settings = new XmlWriterSettings();
settings.Indent = true;
StringBuilder sb = new StringBuilder();
XmlWriter writer = XmlWriter.Create(sb, settings);
XamlWriter.Save(template, writer);
// Display the template.
someControl.Text = sb.ToString();
Here is my CheckBox template:
<?xml version="1.0" encoding="utf-16"?>
<ControlTemplate TargetType="CheckBox" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:s="clr-namespace:System;assembly=mscorlib" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:mwt="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero">
<BulletDecorator Background="#00FFFFFF" SnapsToDevicePixels="True">
<BulletDecorator.Bullet>
<mwt:BulletChrome Background="{TemplateBinding Panel.Background}" BorderBrush="{TemplateBinding Border.BorderBrush}" RenderMouseOver="{TemplateBinding UIElement.IsMouseOver}" RenderPressed="{TemplateBinding ButtonBase.IsPressed}" IsChecked="{TemplateBinding ToggleButton.IsChecked}" />
</BulletDecorator.Bullet>
<ContentPresenter RecognizesAccessKey="True" Content="{TemplateBinding ContentControl.Content}" ContentTemplate="{TemplateBinding ContentControl.ContentTemplate}" ContentStringFormat="{TemplateBinding ContentControl.ContentStringFormat}" Margin="{TemplateBinding Control.Padding}" HorizontalAlignment="{TemplateBinding Control.HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding Control.VerticalContentAlignment}" SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}" />
</BulletDecorator>
<ControlTemplate.Triggers>
<Trigger Property="ContentControl.HasContent">
<Setter Property="FrameworkElement.FocusVisualStyle">
<Setter.Value>
<Style TargetType="IFrameworkInputElement">
<Style.Resources>
<ResourceDictionary />
</Style.Resources>
<Setter Property="Control.Template">
<Setter.Value>
<ControlTemplate>
<Rectangle Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2" Margin="14,0,0,0" SnapsToDevicePixels="True" />
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Setter.Value>
</Setter>
<Setter Property="Control.Padding">
<Setter.Value>
<Thickness>4,0,0,0</Thickness>
</Setter.Value>
</Setter>
<Trigger.Value>
<s:Boolean>True</s:Boolean>
</Trigger.Value>
</Trigger>
<Trigger Property="UIElement.IsEnabled">
<Setter Property="TextElement.Foreground">
<Setter.Value>
<DynamicResource ResourceKey="{x:Static SystemColors.GrayTextBrushKey}" />
</Setter.Value>
</Setter>
<Trigger.Value>
<s:Boolean>False</s:Boolean>
</Trigger.Value>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>

There are tools that extract the original XAML templates from System.Windows.Controls but ultimately, it's down to you as Microsoft as far as I know provide that anywhere. You will need to redefine the entire CheckBox template to achieve what you want.
There are a few websites that list the reflected source code for the .NET Framework assemblies that you could try for an original "generic.xaml" file.