Silverlight实用窍门系列：32.WebClient上传String、下载String、上传Stream流、下载Stream流【附带源码实例】

       Silverlight中我们很多时候需要上传下载数据的时候，在本节将讲述使用WebClient上传String、下载String、上传Stream流、下载Stream流的4个方法和相应的事件。下面我们首先认识一下WebClient类。

        WebClient的主要函数如下：

             •OpenReadAsync 打开流向指定资源的可读流。 
             •OpenWriteAsync 打开一个流以将数据写入指定的资源。这些方法不会阻止调用线程。 
             •DownloadStringAsync 以字符串形式下载位于指定 Uri 的资源。 
             •UploadStringAsync 将指定的字符串上载到指定的资源。这些方法不会阻止调用线程。

        WebClient的主要事件如下：
             •OpenReadCompleted 在异步资源读取操作完成时发生。 
             •OpenWriteCompleted 在打开流以将数据写入资源的异步操作完成时发生。
             •DownloadStringCompleted 在异步资源下载操作完成时发生。 
             •DownloadProgressChanged 在异步下载操作成功传输部分或全部数据后发生。
             •UploadStringCompleted 在异步字符串上载操作完成时发生。  
             •UploadProgressChanged 在异步上载操作成功转换部分或全部数据后发生。

        上面的函数和事件在Silverlight的API中有详细的解释，在本文中不再复述。下面我们来看看一个实例来使用WebClient上传String、下载String、上传Stream流、下载Stream流。

        首先我们准备XAML文件的前台代码，其内有四个按钮，分别代表上传String、下载String、上传Stream流、下载Stream流的按钮。代码如下：

<Grid x:Name="LayoutRoot" Background="White">
        <Canvas Name="lRoot"></Canvas>
        <Button Content="WebClient下载XAP" Height="23" HorizontalAlignment="Left" Margin="410,60,0,0" Name="button1" VerticalAlignment="Top" Width="178" Click="buttonOpenReadAsync_Click"/>
        <Button Content="DownloadStringAsync下载XML" Height="23" HorizontalAlignment="Left" Margin="410,100,0,0" Name="button2" VerticalAlignment="Top" Width="178" Click="buttonDownloadStringAsync_Click"/>
        <Button Content="UploadStringAsync上传String" Height="23" HorizontalAlignment="Left" Margin="410,140,0,0" Name="button3" VerticalAlignment="Top" Width="178" Click="buttonUploadStringAsync_Click"/>
        <Button Content="OpenWriteAsync上传图片" Height="23" HorizontalAlignment="Left" Margin="410,180,0,0" Name="button4" VerticalAlignment="Top" Width="178" Click="buttonOpenWriteAsync_Click"/>
    </Grid>

•上传String操作如下：

        首先建立一个TestHandle.ashx,向这个文件内部写入以下代码以接收Silverlight中上传的String字符。

///<summary>
    /// TestHandle 的摘要说明
    ///</summary>
publicclass TestHandle : IHttpHandler
    {

        publicvoid ProcessRequest(HttpContext context)
        {
            int bytelength = context.Request.ContentLength;
            byte[] inputbytes = context.Request.BinaryRead(bytelength);
            string message = System.Text.Encoding.Default.GetString(inputbytes);
            context.Response.ContentType ="text/plain";
            context.Response.Write("你已经提交数据："+ message);
        }

        publicbool IsReusable
        {
            get
            {
                returnfalse;
            }
        }
    }

        我们再看Silverlight端代码如下：

#region UploadStringAsync上传String
        privatevoid buttonUploadStringAsync_Click(object sender, RoutedEventArgs e)
        {
            //开始调用UploadStringAsync异步上传String
            Appclient.UploadStringAsync(new Uri("http://localhost:3993/TestHandle.ashx", UriKind.RelativeOrAbsolute), "<TD></TD>");
            Appclient.UploadStringCompleted +=new UploadStringCompletedEventHandler(Appclient_UploadStringCompleted);
        }

        void Appclient_UploadStringCompleted(object sender, UploadStringCompletedEventArgs e)
        {
            MessageBox.Show(e.Result);
            Appclient.UploadStringCompleted -=new UploadStringCompletedEventHandler(Appclient_UploadStringCompleted);
        }
        #endregion

•下载String操作如下：

        下载ClientBin目录下已经存在的XML文件

#region DownloadStringAsync下载XML
        privatevoid buttonDownloadStringAsync_Click(object sender, RoutedEventArgs e)
        {
            //开始调用DownloadStringAsync异步下载文档并且读取它
            Appclient.DownloadStringAsync(new Uri("http://localhost:3993/ClientBin/222.xml", UriKind.RelativeOrAbsolute));
            Appclient.DownloadStringCompleted +=new DownloadStringCompletedEventHandler(Appclient_DownloadStringCompleted);
        }
        void Appclient_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
            MessageBox.Show(e.Result);
            Appclient.DownloadStringCompleted -=new DownloadStringCompletedEventHandler(Appclient_DownloadStringCompleted);
        }
        #endregion

•上传Stream操作如下：

        建立一个AddFileHandle.ashx,向这个文件内部写入以下代码以接收Silverlight中上传的Stream数据流。

///<summary>
    /// AddFileHandle 的摘要说明
    ///</summary>
publicclass AddFileHandle : IHttpHandler
    {

        publicvoid ProcessRequest(HttpContext context)
        {
            //获取上传的数据流
using (Stream sr = context.Request.InputStream)
            {
                string filename ="Fir";
                byte[] buffer =newbyte[4096];
                int bytesRead =0;
                //将当前数据流写入ClientBin文件下Fir.jpg文件中
using (FileStream fs = File.Create(context.Server.MapPath("ClientBin/"+ filename +".jpg"), 4096))
                {
                    while ((bytesRead = sr.Read(buffer, 0, buffer.Length)) >0)
                    {
                        //将数据写入文件
                        fs.Write(buffer, 0, bytesRead);
                    }
                }
            }
        }

        publicbool IsReusable
        {
            get
            {
                returnfalse;
            }
        }
    }

        Silverlight读取图片数据，然后传到服务器端（注：此处没有验证传什么数据，如有需要自己调用OpenFileDialog.Filter即可），代码如下：

#region  OpenWriteAsync上传图片
        privatevoid buttonOpenWriteAsync_Click(object sender, RoutedEventArgs e)
        {
            OpenFileDialog dialog =new OpenFileDialog();
            if (dialog.ShowDialog() ==true)
            {
                //开始调用OpenWriteAsync方法上传数据
                Appclient.OpenWriteAsync(new Uri("http://localhost:3993/AddFileHandle.ashx", UriKind.RelativeOrAbsolute), "POST", dialog.File.OpenRead());
                Appclient.OpenWriteCompleted +=new OpenWriteCompletedEventHandler(Appclient_OpenWriteCompleted);
            }
        }
        void Appclient_OpenWriteCompleted(object sender, OpenWriteCompletedEventArgs e)
        {
            //将图片数据流发送到服务器上
            Stream inputStream = e.UserState as Stream;
            Stream outputStream = e.Result;

            byte[] buffer =newbyte[4096];
            int bytesRead =0;
            while ((bytesRead = inputStream.Read(buffer, 0, buffer.Length)) >0)
            {
                outputStream.Write(buffer, 0, bytesRead);
            }
            outputStream.Close();
            inputStream.Close();
            MessageBox.Show("图片上传成功！");
            Appclient.OpenWriteCompleted -=new OpenWriteCompletedEventHandler(Appclient_OpenWriteCompleted);
        }
        #endregion

•下载Stream操作如下：

        本例采用上一节的源码，下载Stream流，然后反射为对象，源码如下：

#region OpenReadAsync下载XAP
privatevoid buttonOpenReadAsync_Click(object sender, RoutedEventArgs e)
{
//1 •使用WebClient下载SLRandarHitTest.xap文件，进行异步读取。
Appclient.OpenReadAsync(new Uri("SLRandarHitTest.xap", UriKind.Relative));
Appclient.OpenReadCompleted +=new OpenReadCompletedEventHandler(Appclient_OpenReadCompleted);
}

void Appclient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
CreateXAPResource("SLRandar.dll", "SLRandar.MainPage", e.Result);
Appclient.OpenReadCompleted -=new OpenReadCompletedEventHandler(Appclient_OpenReadCompleted);
}
///<summary>
/// 创建XAP包的反射实例并且加装到Canvas中
///</summary>
///<param name="dllStr">XAP包中的编译完成的运行代码的DLL文件</param>
///<param name="mainStr">需要实例化的启动页面</param>
///<param name="resultStream">使用WebClient下载到的数据流</param>
privatevoid CreateXAPResource(string dllStr, string mainStr, Stream resultStream)
{
//3 •获取其他包提供的资源流信息
StreamResourceInfo streamResourceInfo = Application.GetResourceStream(new StreamResourceInfo(resultStream as Stream, null), new Uri(dllStr, UriKind.RelativeOrAbsolute));
//4 •对Stream进行反射
AssemblyPart assemblyPart =new AssemblyPart();
Assembly assembly = assemblyPart.Load(streamResourceInfo.Stream);
//5 •(创建实例
var uc = (UserControl)assembly.CreateInstance(mainStr);
lRoot.Children.Clear();
lRoot.Children.Add(uc);
}
#endregion