ProgressBar控件指示长时间运行任务的进度，与slider控件不同，ProgressBar控件不能与用户交互。如果不确定程序要运行多长时间，可以把IsIndeterminate设置true

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <ProgressBar Height="20" IsIndeterminate="True"></ProgressBar>
    </Grid>
</Window>