WPF頁面：

<Grid Margin="10">
    <Grid.RowDefinitions>
        <RowDefinition Height="30"/>
        <RowDefinition/>
        <RowDefinition Height="20"/>
    </Grid.RowDefinitions>
    <TextBlock VerticalAlignment="Center" FontSize="16">版本更新</TextBlock>
    <ProgressBar Name="PJinDu" Grid.Row="1"></ProgressBar>
    <TextBlock Name="TJinDu" Grid.Row="2"></TextBlock>
</Grid>

CS文件

public partial class UpFile : Window
{
    public UpFile()
    {
        InitializeComponent();
        DownLoadFiles();
    }
    private void DownLoadFiles()
    {
        string fpath = "http://網址/文件名.exe";
        string spath = Directory.GetCurrentDirectory() + "\\文件名.exe";
        WebResponse response = null;
        WebRequest request = WebRequest.Create(fpath);
        response = request.GetResponse();
        if (response == null) return;
        PJinDu.Maximum = response.ContentLength;
        ThreadPool.QueueUserWorkItem((obj) =>
        {
            Stream netStream = response.GetResponseStream();
            Stream fileStream = new FileStream(spath, FileMode.Create);
            byte[] read = new byte[1024];
            long progressBarValue = 0;
            int realReadLen = netStream.Read(read, 0, read.Length);
            while (realReadLen > 0)
            {
                fileStream.Write(read, 0, realReadLen);
                progressBarValue += realReadLen;
                PJinDu.Dispatcher.BeginInvoke(new ProgressBarSetter(SetProgressBar), progressBarValue);
                realReadLen = netStream.Read(read, 0, read.Length);
            }
            netStream.Close();
            fileStream.Close();
        }, null);
    }
    public delegate void ProgressBarSetter(double value);
    public void SetProgressBar(double value)
    {
        PJinDu.Value = value;
        TJinDu.Text = "已下載：" + (value / PJinDu.Maximum) * 100 + "%";
        if (value >= PJinDu.Maximum)
        {
            Process isupdate = new Process();
            isupdate.StartInfo.FileName = Directory.GetCurrentDirectory() + "\\文件名.exe";
            isupdate.StartInfo.Arguments = "1";
            isupdate.Start();
            DialogResult = true;
        }
    }
}