WPF user controls are invisible

Question

When I create a custom control in WPF and add it to the window, I don’t see anything where I placed it in the dialog box. That's what I'm doing:

• Create a new WPF application
• Add → New Item ... → Custom Control (WPF): "CustomButton.cs"
• I change the base class CustomButton to Button instead of Control
• Add a CustomButton control to the main window.
• When I launch the application or look at the main window in the designer, I see nothing.

This is what the code looks like.

CustomButton.cs:

public class CustomButton : Button { static CustomButton() { DefaultStyleKeyProperty.OverrideMetadata(typeof(CustomButton), new FrameworkPropertyMetadata(typeof(CustomButton))); } } 

MainWindow.xaml:

 <Window x:Class="WpfApplication1.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MainWindow" Height="350" Width="525" xmlns:my="clr-namespace:WpfApplication1"> <Grid> <my:CustomButton Content="Hello World" x:Name="customButton1" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="150,175,0,0" /> </Grid> </Window> 

Generic.xaml:

 <Style TargetType="{x:Type local:CustomButton}"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type local:CustomButton}"> <Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}"> </Border> </ControlTemplate> </Setter.Value> </Setter> </Style> 

I found two conclusions about what was happening, but nothing clicked. When I added the user control, Visual Studio added Themes / Generic.xaml, but no matter what I try there, I see no difference on the screen. Another thing is that if I comment on the static constructor in CustomButton.cs, the button will suddenly appear in the main window. In all situations, this does not look quite right (for example, if I use the button on the toolbar).

Answer 1

Where is your custom control template?

Speaking

  DefaultStyleKeyProperty.OverrideMetadata(typeof(CustomButton), new FrameworkPropertyMetadata(typeof(CustomButton))); 

You indicate that you want to define your own custom control. I think that if you delete this, you will see your button.

Answer 2

I assume that you have found a solution to your problem in the meantime. However, in this case, someone else is facing the same problem as you: Probably only an explanation of why the user control is not displayed, although all the steps for creating it were performed correctly, like you, this is a missing entry in AssemblyInfo.cs. This file should contain the following entry:

 [assembly: ThemeInfo(ResourceDictionaryLocation.None, ResourceDictionaryLocation.SourceAssembly))] 

Without this entry, the generic.xaml file is ignored, and therefore the default control template is not found, so the control will not receive the control template and therefore will not be displayed. It also explains why your control suddenly appeared when you disabled its static constructor. Line:

 DefaultStyleKeyProperty.OverrideMetadata(typeof(CustomButton), new FrameworkPropertyMetadata(typeof(CustomButton))); 

tells the control to use its own default style instead of inheriting it from its base class. Thus, without this line, CustomButton will simply reuse the default control template for the Button class, as a result of which nothing you write in generic.xaml will affect CustomButton.