DMS/DMS.WPF/Views/Dialogs/ProcessingDialog.xaml

<ui:ContentDialog x:Class="DMS.WPF.Views.Dialogs.ProcessingDialog"
                  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:ui="http://schemas.inkore.net/lib/ui/wpf/modern"
                  xmlns:vmd="clr-namespace:DMS.WPF.ViewModels.Dialogs"
                  Title="{Binding Title}"
                  Background="#fff"
                  d:DataContext="{d:DesignInstance vmd:ProcessingDialogViewModel}"
                  mc:Ignorable="d">
    <Grid Width="360"
          Margin="10">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>

        <TextBlock Grid.Row="0"
                   Margin="0,0,0,20"
                   FontSize="14"
                   TextWrapping="Wrap"
                   FontWeight="Bold"
                   Text="{Binding Message}"
                   HorizontalAlignment="Center" />

        <ui:ProgressRing Grid.Row="1"
                      IsActive="True"
                      Width="50"
                      Height="50"
                      HorizontalAlignment="Center"
                      VerticalAlignment="Center" />
    </Grid>
</ui:ContentDialog>