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        <Button Content="Button" Margin="0,0,10,39.833" BorderThickness="1"  Height="50" VerticalAlignment="Bottom" HorizontalAlignment="Right" Width="115"  >
            
            <Button.Template>
                    <ControlTemplate TargetType="{x:Type Button}">
                    <Grid>
                        <Ellipse Fill="Black">

                        </Ellipse>
                        <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"  >
                            <ContentPresenter.ContentTemplate>
                                <DataTemplate>
                                    <Label Content="{TemplateBinding Content}" Foreground="Red">
                                    </Label>
                                </DataTemplate>
                            </ContentPresenter.ContentTemplate>
                        </ContentPresenter>
                    </Grid>
                </ControlTemplate>
            </Button.Template>
        </Button>

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <Style x:Key="FocusVisual">
            <Setter Property="Control.Template">
                <Setter.Value>
                    <ControlTemplate>
                        <Rectangle Margin="2" SnapsToDevicePixels="true" Stroke="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}" StrokeThickness="1" StrokeDashArray="1 2"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        <SolidColorBrush x:Key="Button.Static.Background" Color="#FFDDDDDD"/>
        <SolidColorBrush x:Key="Button.Static.Border" Color="#FF707070"/>
        <SolidColorBrush x:Key="Button.MouseOver.Background" Color="#FFBEE6FD"/>
        <SolidColorBrush x:Key="Button.MouseOver.Border" Color="#FF3C7FB1"/>
        <SolidColorBrush x:Key="Button.Pressed.Background" Color="#FFC4E5F6"/>
        <SolidColorBrush x:Key="Button.Pressed.Border" Color="#FF2C628B"/>
        <SolidColorBrush x:Key="Button.Disabled.Background" Color="#FFF4F4F4"/>
        <SolidColorBrush x:Key="Button.Disabled.Border" Color="#FFADB2B5"/>
        <SolidColorBrush x:Key="Button.Disabled.Foreground" Color="#FF838383"/>
        <Style x:Key="ButtonStyle1" TargetType="{x:Type Button}">
            <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
            <Setter Property="Background" Value="{StaticResource Button.Static.Background}"/>
            <Setter Property="BorderBrush" Value="{StaticResource Button.Static.Border}"/>
            <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.ControlTextBrushKey}}"/>
            <Setter Property="BorderThickness" Value="1"/>
            <Setter Property="HorizontalContentAlignment" Value="Center"/>
            <Setter Property="VerticalContentAlignment" Value="Center"/>
            <Setter Property="Padding" Value="1"/>
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type Button}">
                        <Grid>
                            <Ellipse Fill="{TemplateBinding Background}"></Ellipse>
                            <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"></ContentPresenter>
                        </Grid>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>
    <Grid>
        <Button Content="Hello" Width="200" Height="200" Background="Yellow" Style="{DynamicResource ButtonStyle1}"></Button>
    </Grid>
</Window>