WPF ProgressBar实现实时进度效果

<Page x:Class="WpfBrowserAppDrill.ProgressBarPage"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
  xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
  mc:Ignorable="d" 
Title="ProgressBarPage" Loaded="Page_Loaded">


 <Grid>
  <Button Margin="10" Click="Button_Click" VerticalAlignment="Top" Height="23" Width="100">进度条控制</Button>
  <TextBlock Name="txtJD" VerticalAlignment="Top" HorizontalAlignment="Center" Margin="50">当前进度：</TextBlock>
  <ProgressBar Height="20" HorizontalAlignment="Center" Margin="8,167,0,0" 
Name="pb_import" VerticalAlignment="Top" Width="500" />
 </Grid>
</Page>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Threading;


namespace WpfBrowserAppDrill
{
 /// <summary>
 /// ProgressBarPage.xaml 的交互逻辑
 /// </summary>
 public partial class ProgressBarPage : Page
 {


  public ProgressBarPage()
  {
   InitializeComponent(); 
  } 


  private void beginImport() 
  {
   double value = 0;
   double total = 100d;//得到循环次数
   while (value < total)
   {
    double jd = Math.Round(((value + 1) * (pb_import.Maximum / total)), 4);


    pb_import.Dispatcher.Invoke(new Action<System.Windows.DependencyProperty, object>(pb_import.SetValue),
     System.Windows.Threading.DispatcherPriority.Background,
     ProgressBar.ValueProperty,
     jd);
    //这里是加数据或费时的操作，我这里让它挂起300毫秒
    Thread.Sleep(300);
    txtJD.Text = "当前的进度是:" + (value + 1) + "(实际值)" + jd + "(百分比)";
    value++;
   }
  }
  private void Button_Click(object sender, RoutedEventArgs e)
  {
   beginImport();
   ////new Thread(new ThreadStart(beginImport)).Start();


  }


  private void Page_Loaded(object sender, RoutedEventArgs e)
  {  
   pb_import.Maximum = 100;
   pb_import.Value = 0; 


  } 


 }
}