---

<Button Content="Нажми меня"
        Width="150"
        Height="50"
        Background="Gray"
        Click="Button_Click">

    <Button.Template>
        <ControlTemplate TargetType="Button">
            <Border Background="{TemplateBinding Background}"
                    CornerRadius="5">
                <ContentPresenter
                    HorizontalAlignment="Center"
                    VerticalAlignment="Center"/>
            </Border>
        </ControlTemplate>
    </Button.Template>
</Button>