csharp-progressbar/MainWindow.xaml

<Window x:Name="Processing" x:Class="ProgressBar.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"
        mc:Ignorable="d"
        Title="Processing..."
        HorizontalAlignment="Center"
        VerticalAlignment="Center"
        Width="360"
        Height="100"
        ResizeMode="NoResize"
        WindowStartupLocation="CenterScreen" Topmost="True">
    <Viewbox HorizontalAlignment="Center" VerticalAlignment="Center">
        <Grid VerticalAlignment="Center" HorizontalAlignment="Center">
            <Grid.RowDefinitions>
                <RowDefinition Height="60" Name="RowActions"/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"/>
                <ColumnDefinition Width="150"/>
            </Grid.ColumnDefinitions>

            <Button
                x:Name="BtnStart"
                Content="Start processing"
                Grid.Column="1"
                Margin="6,20,4,20"
                Click="BtnStart_Click"
                VerticalAlignment="Center"
                />

            <Grid Margin="5,5,0,0">
                <Grid.RowDefinitions>
                    <RowDefinition Height="20" />
                </Grid.RowDefinitions>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="30"/>
                    <ColumnDefinition Width="Auto"/>
                </Grid.ColumnDefinitions>

                <TextBox
                    x:Name="Amount"
                    Grid.Column="0"
                    Text="{Binding Countdown, FallbackValue=1, Mode=TwoWay, NotifyOnTargetUpdated=True, NotifyOnSourceUpdated=True, NotifyOnValidationError=True, StringFormat=\{0:D\}, TargetNullValue=1, UpdateSourceTrigger=LostFocus}"
                    MaxLength="3"
                    TextAlignment="Right"
                    BorderBrush="{x:Null}"
                    Background="{x:Null}"
                    SelectionBrush="{x:Null}"
                    IsEnabled="False"
                />
                <Label
                    x:Name="AmountLabel"
                    Grid.Column="1"
                    Content="seconds to process" Padding="5,0"
                />
            </Grid>
            <Slider
                x:Name="Slider"
                VerticalAlignment="Bottom"
                Value="{Binding Countdown, FallbackValue=1, Mode=TwoWay, NotifyOnTargetUpdated=True, NotifyOnSourceUpdated=True, NotifyOnValidationError=True, TargetNullValue=1, ValidatesOnDataErrors=True, ValidatesOnExceptions=True}"
                Margin="10,0,0,10"
                ValueChanged="Slider_ValueChanged"
                Minimum="1"
                Maximum="3600"
                SmallChange="1"
                />

            <ProgressBar
                x:Name="ProgressBar"
                Grid.Column="0"
                Grid.ColumnSpan="2"
                Grid.Row="0"
                Value="0"
                Maximum="100"
                Height="20"
                Margin="10,5"
                Visibility="Hidden"
                />

            <Button
                x:Name="ButtonDone"
                Grid.ColumnSpan="2"
                Grid.RowSpan="2"
                AutomationProperties.Name="ButtonDone"
                Content="Done processing. Click to confirm and close."
                Click="ButtonDone_Click"
                Visibility="Hidden"
                VerticalAlignment="Center"
                HorizontalAlignment="Center"
                Padding="5"
                />

        </Grid>
    </Viewbox>
</Window>