modernkeepass/Win10App/ResourceDictionaries/NoBorderButtonStyle.xaml

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <!-- Default style for Windows.UI.Xaml.Controls.Button -->
    <Style TargetType="Button" x:Key="NoBorderButtonStyle">
        <Setter Property="Background" Value="{ThemeResource ButtonBackgroundThemeBrush}" />
        <Setter Property="Foreground" Value="{ThemeResource ButtonForegroundThemeBrush}"/>
        <Setter Property="BorderBrush" Value="{ThemeResource ButtonBorderThemeBrush}" />
        <Setter Property="BorderThickness" Value="{ThemeResource ButtonBorderThemeThickness}" />
        <Setter Property="Padding" Value="12,4,12,4" />
        <Setter Property="HorizontalAlignment" Value="Left" />
        <Setter Property="VerticalAlignment" Value="Center" />
        <Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}" />
        <Setter Property="FontWeight" Value="SemiBold" />
        <Setter Property="FontSize" Value="{ThemeResource ControlContentThemeFontSize}" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="Button">
                    <Grid>
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Normal" />
                                <VisualState x:Name="PointerOver">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                                       Storyboard.TargetProperty="Background">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ButtonPointerOverBackgroundThemeBrush}" />
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
                                                                       Storyboard.TargetProperty="Foreground">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ButtonPointerOverForegroundThemeBrush}" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Pressed">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                                       Storyboard.TargetProperty="Background">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ButtonPressedBackgroundThemeBrush}" />
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
                                                                       Storyboard.TargetProperty="Foreground">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ButtonPressedForegroundThemeBrush}" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Disabled">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                                       Storyboard.TargetProperty="Background">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource AppBarBackgroundThemeBrush}" />
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="Border"
                                                                       Storyboard.TargetProperty="BorderBrush">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ButtonDisabledBorderThemeBrush}" />
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetName="ContentPresenter"
                                                                       Storyboard.TargetProperty="Foreground">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource ButtonDisabledForegroundThemeBrush}" />
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="FocusStates">
                                <VisualState x:Name="Focused">
                                    <Storyboard>
                                        <DoubleAnimation Storyboard.TargetName="FocusVisualWhite"
                                                         Storyboard.TargetProperty="Opacity"
                                                         To="1"
                                                         Duration="0" />
                                        <DoubleAnimation Storyboard.TargetName="FocusVisualBlack"
                                                         Storyboard.TargetProperty="Opacity"
                                                         To="1"
                                                         Duration="0" />
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Unfocused" />
                                <VisualState x:Name="PointerFocused" />
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Border x:Name="Border"
                                Background="{TemplateBinding Background}"
                                BorderBrush="{TemplateBinding BorderBrush}"
                                BorderThickness="{TemplateBinding BorderThickness}"
                                Margin="0">
                            <ContentPresenter x:Name="ContentPresenter"
                                              Content="{TemplateBinding Content}"
                                              ContentTransitions="{TemplateBinding ContentTransitions}"
                                              ContentTemplate="{TemplateBinding ContentTemplate}"
                                              Margin="{TemplateBinding Padding}"
                                              HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
                                              VerticalAlignment="{TemplateBinding VerticalContentAlignment}" 
                                              AutomationProperties.AccessibilityView="Raw"/>
                        </Border>
                        <Rectangle x:Name="FocusVisualWhite"
                                   IsHitTestVisible="False"
                                   Stroke="{ThemeResource FocusVisualWhiteStrokeThemeBrush}"
                                   StrokeEndLineCap="Square"
                                   StrokeDashArray="1,1"
                                   Opacity="0"
                                   StrokeDashOffset="1.5" />
                        <Rectangle x:Name="FocusVisualBlack"
                                   IsHitTestVisible="False"
                                   Stroke="{ThemeResource FocusVisualBlackStrokeThemeBrush}"
                                   StrokeEndLineCap="Square"
                                   StrokeDashArray="1,1"
                                   Opacity="0"
                                   StrokeDashOffset="0.5" />
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</ResourceDictionary>