ComboBox cannot be opened after appying style

Question

I used XamlPadX to copy the defaultstyle of the ComboBox and pasted it into my app ressources.

Now after that I cannot open the combobox anymore. If I click on the dropdown button, nothing happens.

Another thing is bugging me. Altough the app compiles and runs, the designer shows me an error:

"Value 'Control.Template' cannot be assigned to property 'Property'. 'IFrameworkInputElement' type does not have a matching DependencyObjectType.".

on the following line:

<ComboBox Name="modifier" SelectedIndex="0" Style="{DynamicResource MyComboStyle}">
       <ComboBoxItem>1</ComboBoxItem>
       <ComboBoxItem>2</ComboBoxItem>
       <ComboBoxItem>3</ComboBoxItem>
</ComboBox>

Because of this the designer doesn't show me the control, but it shows up properly when the app is run.

But when I declare the ComboBox as its own control there is no designer error:

<ComboBox x:Class="ModifierControl"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    
    Style="{DynamicResource MyComboStyle}" >
</ComboBox>

Then no designer error is shown.

Answer 1

Here's the template for ComboBox picked directly from Blend. Let me know if it works.

<Window
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:Microsoft_Windows_Themes="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Classic"
    x:Class="MyComboBoxStyle.MainWindow"
    x:Name="Window"
    Title="MainWindow"
    Width="640" Height="480">

    <Window.Resources>
        <Style x:Key="MyComboBoxStyle" TargetType="{x:Type ComboBox}">
            <Setter Property="FocusVisualStyle">
                <Setter.Value>
                    <Style>
                        <Setter Property="Control.Template">
                            <Setter.Value>
                                <ControlTemplate>
                                    <Rectangle Stroke="Black" StrokeDashArray="1 2" StrokeThickness="1" Margin="4,4,21,4" SnapsToDevicePixels="True"/>
                                </ControlTemplate>
                            </Setter.Value>
                        </Setter>
                    </Style>
                </Setter.Value>
            </Setter>
            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.WindowTextBrushKey}}"/>
            <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"/>
            <Setter Property="Margin" Value="0"/>
            <Setter Property="Padding" Value="2,1"/>
            <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
            <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
            <Setter Property="ScrollViewer.CanContentScroll" Value="True"/>
            <Setter Property="VerticalContentAlignment" Value="Center"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ComboBox}">
                        <Border SnapsToDevicePixels="True" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
                            <Grid>
                                <Microsoft_Windows_Themes:ClassicBorderDecorator x:Name="Border" Background="{TemplateBinding Background}" BorderStyle="Sunken" BorderThickness="2">
                                    <Microsoft_Windows_Themes:ClassicBorderDecorator.BorderBrush>
                                        <SolidColorBrush/>
                                    </Microsoft_Windows_Themes:ClassicBorderDecorator.BorderBrush>
                                    <Popup x:Name="PART_Popup" AllowsTransparency="True" IsOpen="{TemplateBinding IsDropDownOpen}" Placement="Bottom" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Focusable="False">
                                        <Microsoft_Windows_Themes:SystemDropShadowChrome x:Name="Shdw" MaxHeight="{TemplateBinding MaxDropDownHeight}" MinWidth="{Binding ActualWidth, ElementName=Border}" Color="Transparent">
                                            <Border x:Name="DropDownBorder" Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}" BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" BorderThickness="1">
                                                <ScrollViewer>
                                                    <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" KeyboardNavigation.DirectionalNavigation="Contained"/>
                                                </ScrollViewer>
                                            </Border>
                                        </Microsoft_Windows_Themes:SystemDropShadowChrome>
                                    </Popup>
                                </Microsoft_Windows_Themes:ClassicBorderDecorator>
                                <DockPanel Margin="2">
                                    <FrameworkElement Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" DockPanel.Dock="Right"/>
                                    <Border x:Name="SelectedItemBorder" Margin="{TemplateBinding Padding}">
                                        <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" Content="{TemplateBinding SelectionBoxItem}" ContentStringFormat="{TemplateBinding SelectionBoxItemStringFormat}" ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"/>
                                    </Border>
                                </DockPanel>
                                <ToggleButton Margin="2" MinHeight="0" MinWidth="0" Width="Auto" Focusable="False" ClickMode="Press" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}">
                                    <ToggleButton.Style>
                                        <Style TargetType="{x:Type ToggleButton}">
                                            <Setter Property="MinWidth" Value="0"/>
                                            <Setter Property="MinHeight" Value="0"/>
                                            <Setter Property="Width" Value="NaN"/>
                                            <Setter Property="Height" Value="NaN"/>
                                            <Setter Property="Background" Value="Transparent"/>
                                            <Setter Property="BorderBrush">
                                                <Setter.Value>
                                                    <SolidColorBrush/>
                                                </Setter.Value>
                                            </Setter>
                                            <Setter Property="BorderThickness" Value="2"/>
                                            <Setter Property="Template">
                                                <Setter.Value>
                                                    <ControlTemplate TargetType="{x:Type ToggleButton}">
                                                        <DockPanel SnapsToDevicePixels="True" Background="{TemplateBinding Background}" LastChildFill="False">
                                                            <Microsoft_Windows_Themes:ClassicBorderDecorator x:Name="Border" Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" DockPanel.Dock="Right" Background="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" BorderBrush="{TemplateBinding BorderBrush}" BorderStyle="AltRaised" BorderThickness="{TemplateBinding BorderThickness}">
                                                                <Path Fill="{TemplateBinding Foreground}" HorizontalAlignment="Center" VerticalAlignment="Center" Data="M0,0L3.5,4 7,0z"/>
                                                            </Microsoft_Windows_Themes:ClassicBorderDecorator>
                                                        </DockPanel>
                                                        <ControlTemplate.Triggers>
                                                            <Trigger Property="IsChecked" Value="True">
                                                                <Setter Property="BorderStyle" TargetName="Border" Value="AltPressed"/>
                                                            </Trigger>
                                                        </ControlTemplate.Triggers>
                                                    </ControlTemplate>
                                                </Setter.Value>
                                            </Setter>
                                            <Style.Triggers>
                                                <Trigger Property="IsEnabled" Value="False">
                                                    <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
                                                </Trigger>
                                            </Style.Triggers>
                                        </Style>
                                    </ToggleButton.Style>
                                </ToggleButton>
                            </Grid>
                        </Border>
                        <ControlTemplate.Triggers>
                            <MultiTrigger>
                                <MultiTrigger.Conditions>
                                    <Condition Property="IsSelectionBoxHighlighted" Value="True"/>
                                    <Condition Property="IsDropDownOpen" Value="False"/>
                                </MultiTrigger.Conditions>
                                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}"/>
                            </MultiTrigger>
                            <Trigger Property="IsSelectionBoxHighlighted" Value="True">
                                <Setter Property="Background" TargetName="SelectedItemBorder" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}"/>
                            </Trigger>
                            <Trigger Property="HasItems" Value="False">
                                <Setter Property="MinHeight" TargetName="DropDownBorder" Value="95"/>
                            </Trigger>
                            <Trigger Property="IsEnabled" Value="False">
                                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                                <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
                            </Trigger>
                            <Trigger Property="IsGrouping" Value="True">
                                <Setter Property="ScrollViewer.CanContentScroll" Value="False"/>
                            </Trigger>
                            <Trigger Property="HasDropShadow" SourceName="PART_Popup" Value="True">
                                <Setter Property="Margin" TargetName="Shdw" Value="0,0,5,5"/>
                                <Setter Property="Color" TargetName="Shdw" Value="#71000000"/>
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
            <Style.Triggers>
                <Trigger Property="IsEditable" Value="True">
                    <Setter Property="IsTabStop" Value="False"/>
                    <Setter Property="Padding" Value="1"/>
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type ComboBox}">
                                <Border SnapsToDevicePixels="True" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
                                    <Grid>
                                        <Microsoft_Windows_Themes:ClassicBorderDecorator x:Name="Border" Background="{TemplateBinding Background}" BorderStyle="Sunken" BorderThickness="2">
                                            <Microsoft_Windows_Themes:ClassicBorderDecorator.BorderBrush>
                                                <SolidColorBrush/>
                                            </Microsoft_Windows_Themes:ClassicBorderDecorator.BorderBrush>
                                            <Popup x:Name="PART_Popup" AllowsTransparency="True" IsOpen="{TemplateBinding IsDropDownOpen}" Placement="Bottom" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}" Focusable="False">
                                                <Microsoft_Windows_Themes:SystemDropShadowChrome x:Name="Shdw" MaxHeight="{TemplateBinding MaxDropDownHeight}" MinWidth="{Binding ActualWidth, ElementName=Border}" Color="Transparent">
                                                    <Border x:Name="DropDownBorder" Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}" BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" BorderThickness="1">
                                                        <ScrollViewer>
                                                            <ItemsPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" KeyboardNavigation.DirectionalNavigation="Contained"/>
                                                        </ScrollViewer>
                                                    </Border>
                                                </Microsoft_Windows_Themes:SystemDropShadowChrome>
                                            </Popup>
                                        </Microsoft_Windows_Themes:ClassicBorderDecorator>
                                        <ToggleButton Margin="2" MinHeight="0" MinWidth="0" Width="Auto" Focusable="False" ClickMode="Press" IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}">
                                            <ToggleButton.Style>
                                                <Style TargetType="{x:Type ToggleButton}">
                                                    <Setter Property="MinWidth" Value="0"/>
                                                    <Setter Property="MinHeight" Value="0"/>
                                                    <Setter Property="Width" Value="NaN"/>
                                                    <Setter Property="Height" Value="NaN"/>
                                                    <Setter Property="Background" Value="Transparent"/>
                                                    <Setter Property="BorderBrush">
                                                        <Setter.Value>
                                                            <SolidColorBrush/>
                                                        </Setter.Value>
                                                    </Setter>
                                                    <Setter Property="BorderThickness" Value="2"/>
                                                    <Setter Property="Template">
                                                        <Setter.Value>
                                                            <ControlTemplate TargetType="{x:Type ToggleButton}">
                                                                <DockPanel SnapsToDevicePixels="True" Background="{TemplateBinding Background}" LastChildFill="False">
                                                                    <Microsoft_Windows_Themes:ClassicBorderDecorator x:Name="Border" Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" DockPanel.Dock="Right" Background="{DynamicResource {x:Static SystemColors.ControlBrushKey}}" BorderBrush="{TemplateBinding BorderBrush}" BorderStyle="AltRaised" BorderThickness="{TemplateBinding BorderThickness}">
                                                                        <Path Fill="{TemplateBinding Foreground}" HorizontalAlignment="Center" VerticalAlignment="Center" Data="M0,0L3.5,4 7,0z"/>
                                                                    </Microsoft_Windows_Themes:ClassicBorderDecorator>
                                                                </DockPanel>
                                                                <ControlTemplate.Triggers>
                                                                    <Trigger Property="IsChecked" Value="True">
                                                                        <Setter Property="BorderStyle" TargetName="Border" Value="AltPressed"/>
                                                                    </Trigger>
                                                                </ControlTemplate.Triggers>
                                                            </ControlTemplate>
                                                        </Setter.Value>
                                                    </Setter>
                                                    <Style.Triggers>
                                                        <Trigger Property="IsEnabled" Value="False">
                                                            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}"/>
                                                        </Trigger>
                                                    </Style.Triggers>
                                                </Style>
                                            </ToggleButton.Style>
                                        </ToggleButton>
                                        <DockPanel Margin="2">
                                            <FrameworkElement Width="{DynamicResource {x:Static SystemParameters.VerticalScrollBarWidthKey}}" DockPanel.Dock="Right"/>
                                            <TextBox x:Name="PART_EditableTextBox" Margin="{TemplateBinding Padding}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" IsReadOnly="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}}">
                                                <TextBox.Style>
                                                    <Style TargetType="{x:Type TextBox}">
                                                        <Setter Property="OverridesDefaultStyle" Value="True"/>
                                                        <Setter Property="AllowDrop" Value="True"/>
                                                        <Setter Property="MinWidth" Value="0"/>
                                                        <Setter Property="MinHeight" Value="0"/>
                                                        <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
                                                        <Setter Property="Template">
                                                            <Setter.Value>
                                                                <ControlTemplate TargetType="{x:Type TextBox}">
                                                                    <ScrollViewer x:Name="PART_ContentHost" Background="Transparent" Focusable="False" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
                                                                </ControlTemplate>
                                                            </Setter.Value>
                                                        </Setter>
                                                    </Style>
                                                </TextBox.Style>
                                            </TextBox>
                                        </DockPanel>
                                    </Grid>
                                </Border>
                                <ControlTemplate.Triggers>
                                    <Trigger Property="HasItems" Value="False">
                                        <Setter Property="MinHeight" TargetName="DropDownBorder" Value="95"/>
                                    </Trigger>
                                    <Trigger Property="HasDropShadow" SourceName="PART_Popup" Value="True">
                                        <Setter Property="Margin" TargetName="Shdw" Value="0,0,5,5"/>
                                        <Setter Property="Color" TargetName="Shdw" Value="#71000000"/>
                                    </Trigger>
                                    <Trigger Property="IsEnabled" Value="False">
                                        <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}"/>
                                        <Setter Property="Background" Value="{DynamicResource {x:Static SystemColors.ControlBrushKey}}"/>
                                    </Trigger>
                                    <Trigger Property="IsGrouping" Value="True">
                                        <Setter Property="ScrollViewer.CanContentScroll" Value="False"/>
                                    </Trigger>
                                </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>

    <Grid x:Name="LayoutRoot">
        <ComboBox HorizontalAlignment="Left" Margin="111,156,0,0" Style="{DynamicResource MyComboBoxStyle}" VerticalAlignment="Top" Width="197" Height="25"/>
    </Grid>
</Window>

Answer 2

The first thing that comes to my mind would be to change the line mentioned below to access the resource as StaticResource. This will give a compilation error if the compiler didn't find the resource. Also, do make sure to define the the resource before the line where you actually use it.

Style="{DynamicResource MyComboStyle}"