SizeToContent paints an unwanted border

c#, sizetocontent, wpf

Solution

Using this tool (it's good, btw) I found that the `Border` control of the `Window` (it's immediate child) doesn't fill the whole window, leaving that "border", which is actually the background of the `Window` control.

I've found a workaround. `Width` and `Height` of the `Border` are `NaN`. If you set those to an integer value, the "border" disappears.

Let's use the values of `ActualWidth` and `ActualHeight`, but rounded to an integer.

Define the converter:

C#

[ValueConversion(typeof(double), typeof(double))]
public class RoundConverter : IValueConverter {
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
        return Math.Ceiling((double)value);
    }
    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture) {
        return value;
    }
}

XAML (remember to include your namespace, in this case "c")

<c:RoundConverter x:Key="RoundConverter"/>

Then create a style binding the size to the actual size using the converter. It's important to use a Key, so it won't apply to every `Border` (most controls use it):

<Style TargetType="{x:Type Border}" x:Key="WindowBorder">
    <Setter Property="Width" Value="{Binding RelativeSource={RelativeSource Self}, Path=ActualWidth, Converter={StaticResource RoundConverter}}"/>
    <Setter Property="Height" Value="{Binding RelativeSource={RelativeSource Self}, Path=ActualHeight, Converter={StaticResource RoundConverter}}"/>
</Style>

Finally, apply this style to the first child of the window (the `Border` control):

private void Window_Loaded(object sender, RoutedEventArgs e) {
    GetVisualChild(0).SetValue(StyleProperty, Application.Current.Resources["WindowBorder"]);
}

If someone can do this in a simpler way, please share too.

Problem

Original source