BlockWindow.xaml

<local:RoundedWindow x:Class="ZipImageViewer.BlockWindow" x:Name="BlockWin"
        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:ZipImageViewer" WindowStartupLocation="CenterOwner" CloseBehavior="FadeOutAndClose"
        Background="{StaticResource BackgroundLightBrush}" Foreground="{StaticResource ForegroundBrush}"
        mc:Ignorable="d" Height="170" Width="260" ShowInTaskbar="False" Loaded="BlockWin_Loaded" Closing="BlockWin_Closing"
        ResizeMode="NoResize" Topmost="True">
    <Window.Resources>
        <!--<local:CenterParentConverter x:Key="CenterParentConverter"/>-->
    </Window.Resources>
    <!--<Window.Left>
        <MultiBinding Converter="{StaticResource CenterParentConverter}" Mode="OneWayToSource">
            <Binding RelativeSource="{RelativeSource Self}" Path="Owner.Left"/>
            <Binding RelativeSource="{RelativeSource Self}" Path="Owner.Width"/>
            <Binding RelativeSource="{RelativeSource Self}" Path="Width"/>
        </MultiBinding>
    </Window.Left>
    <Window.Top>
        <MultiBinding Converter="{StaticResource CenterParentConverter}" Mode="OneWayToSource">
            <Binding RelativeSource="{RelativeSource Self}" Path="Owner.Top"/>
            <Binding RelativeSource="{RelativeSource Self}" Path="Owner.Height"/>
            <Binding RelativeSource="{RelativeSource Self}" Path="Height"/>
        </MultiBinding>
    </Window.Top>-->
    <Grid x:Name="grid" RenderTransformOrigin="0.5,0.5" Margin="0 0 0 15">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <TextBlock x:Name="T_Title" HorizontalAlignment="Center" VerticalAlignment="Top" FontWeight="Bold"
                   Text="{Binding MessageTitle, ElementName=BlockWin, Mode=OneWay}"/>
        <TextBlock Grid.Row="1" x:Name="TB_Message" HorizontalAlignment="Stretch" TextWrapping="Wrap" FontSize="10" Margin="5 10"
                   Text="{Binding MessageBody, ElementName=BlockWin, Mode=OneWay}"/>
        <ProgressBar Grid.Row="2" x:Name="PB_Message" Height="{Binding FontSize, ElementName=BlockWin, Mode=OneWay}" Margin="5 0"
                         Value="{Binding Percentage, ElementName=BlockWin, Mode=OneWay}">
            <ProgressBar.Style>
                <Style TargetType="ProgressBar">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding Percentage, ElementName=BlockWin, Mode=OneWay}" Value="-1">
                            <Setter Property="IsIndeterminate" Value="True" />
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </ProgressBar.Style>
        </ProgressBar>
    </Grid>
</local:RoundedWindow>