In WPF, how do I give my custom control a default style to be used in Design Mode?

问题

I have created a custom WPF control. The control acts as a container with various regions (so it can work like a master page).

The style for this control is loaded at runtime from a separate resource dictionary as follows:

<Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="/MyApp.Application;component/Themes/Theme.xaml" x:Name="theme"/>
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>

My custom control's style looks as follows...

<Style TargetType="{x:Type shareduc:EditControlMaster}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type shareduc:EditControlMaster}">
                <Grid>
                    <Grid.ColumnDefinitions></Grid.ColumnDefinitions>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="auto"></RowDefinition>
                        <RowDefinition Height="*"></RowDefinition>
                    </Grid.RowDefinitions>

                    <Border BorderBrush="{DynamicResource xxBorderBrush}" 
                                BorderThickness="0,1,0,1" Background="White" Grid.Row="0">
                        <Grid >
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="auto"></ColumnDefinition>
                                <ColumnDefinition Width="*"></ColumnDefinition>
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="auto"></RowDefinition>
                                <RowDefinition Height="auto"></RowDefinition>
                            </Grid.RowDefinitions>

                            <ContentPresenter Grid.Row="0" Grid.Column="0" Grid.RowSpan="2" Margin="10" Content="{TemplateBinding Image}"  />
                            <ContentPresenter Grid.Row="0" Grid.Column="1" Margin="2" Content="{TemplateBinding Title}"  />
                            <ContentPresenter Grid.Row="1" Grid.Column="1" Margin="2" Content="{TemplateBinding Abstract}"  />
                        </Grid>
                    </Border>

                    <ContentPresenter Grid.Row="1" Margin="2" Content="{TemplateBinding Content}" />

                </Grid>

            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

The problem is that this style is only loaded at Runtime. So in Design Mode my control does not have any style and does not have any size or layout. How can I give my control a default style for Design Mode?

Update: I'm making some progress... it appears I can specify a default theme to use in a file called Themes\Generic.xaml. This works fine in a small sample project, but for some reason my VS2008 designer stays blank when I do the same thing in my actual project... Help? :(

Note that my custom control's code looks as follows:

public partial class EditControlMaster : Control
    {
        static EditControlMaster()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(EditControlMaster),
              new FrameworkPropertyMetadata(typeof(EditControlMaster)));
        }

        public object Title
        {
            get { return (object)GetValue(TitleProperty); }
            set { SetValue(TitleProperty, value); }
        }

        public static readonly DependencyProperty TitleProperty =
          DependencyProperty.Register("Title", typeof(object),
          typeof(EditControlMaster), new UIPropertyMetadata());



        public object Image
        {
            get { return (object)GetValue(ImageProperty); }
            set { SetValue(ImageProperty, value); }
        }

        public static readonly DependencyProperty ImageProperty =
          DependencyProperty.Register("Image", typeof(object),
          typeof(EditControlMaster), new UIPropertyMetadata());


        public object Abstract
        {
            get { return (object)GetValue(AbstractProperty); }
            set { SetValue(AbstractProperty, value); }
        }

        public static readonly DependencyProperty AbstractProperty =
          DependencyProperty.Register("Abstract", typeof(object),
          typeof(EditControlMaster), new UIPropertyMetadata());

        public object Content
        {
            get { return (object)GetValue(ContentProperty); }
            set { SetValue(ContentProperty, value); }
        }

        public static readonly DependencyProperty ContentProperty =
          DependencyProperty.Register("Content", typeof(object),
          typeof(EditControlMaster), new UIPropertyMetadata());
    }

回答1:

Through lots of poking around project files I have figured out what was wrong!

Themes\Generic.xaml contains your control's default Style. This is fine.

Your Assembly.cs file needs to contain the following attribute:

[assembly: ThemeInfo(
    ResourceDictionaryLocation.None, //where theme specific resource dictionaries are located
    //(used if a resource is not found in the page, 
    // or application resource dictionaries)
    ResourceDictionaryLocation.SourceAssembly //where the generic resource dictionary is located
    //(used if a resource is not found in the page, 
    // app, or any theme specific resource dictionaries)
)]

Voila! The VS2008 designer works!

回答2:

Did you try

public EditControlMaster()
{
  DefaultStyleKey = typeof(EditControlMaster);
}

as part of the constructor?

回答3:

Try moving the style to a standard place.

Add / New Item / Custom Control(WPF) / "MyDummyControl"
now place your style in "Themes/Generic.xaml" that was created
remove "MyDummyControl" files and style
remove your Theme.xaml, and MergedDictionaries

回答4:

One more thing, in my experience, using DynamicResource in a style defined in themes\generic.xaml (like you did for the Border) does not work (at least, does not work always). You should consider changing that to a StaticResource lookup.

来源：https://stackoverflow.com/questions/1232584/in-wpf-how-do-i-give-my-custom-control-a-default-style-to-be-used-in-design-mod

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styles