Silverlight请求HttpHandler获取数据

1）在initParams配置参数“UploadHandlerName=Ajax/HttpUploadHandler.ashx”。

2）在Silverlight程序中的添加文件的方法中编写请求代码。这块值得注意的，一是路径，二是获取到数据后，要使用this.Dispatcher.BeginInvoke来更新界面（否则会出异常）。具体代码如下：

public class RequestStates
{
    ///

    /// 当前请求
    ///

    public HttpWebRequest CurrentWebRequest { get; set; }
    ///

    /// 当前用户文件
    ///

    public UserFile CurrentUserFile { get; set; }
}
private void AddFile(FileInfo file)
{
    string fileName = file.Name;
    var userFile = new UserFile { FileName = file.Name, FileStream = file.OpenRead() };

    if (!string.IsNullOrEmpty(Configuration.Instance.CheckExtensionsHandlerName))
    {
        //获取处理的Handler类的路径
        UriBuilder httpHandlerUrlBuilder = new UriBuilder(new CustomUri(Configuration.Instance.CheckExtensionsHandlerName));
        //设置请求的参数
        httpHandlerUrlBuilder.Query = string.Format("{2}file={0}&Extension={1}", HttpUtility.UrlEncode(userFile.FileName), HttpUtility.UrlEncode(Path.GetExtension(userFile.FileName)), string.IsNullOrEmpty(httpHandlerUrlBuilder.Query) ? string.Empty : httpHandlerUrlBuilder.Query.Remove(0, 1) + "&");
        //创建请求
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(httpHandlerUrlBuilder.Uri);
        request.Method = "POST";
        //设置自定义信息，用于异步请求
        var requestStates = new RequestStates()
                                 {
                                     CurrentUserFile = userFile,
                                     CurrentWebRequest = request
                                 };
        //开始异步请求
        request.BeginGetRequestStream(new AsyncCallback(RequestReady), requestStates);
    }
    else
    {
        _files.Add(userFile);
    }
}
private void RequestReady(IAsyncResult asynchronousResult)
{
    var requestStates = (RequestStates)asynchronousResult.AsyncState;
    HttpWebRequest webRequest = requestStates.CurrentWebRequest;
    Stream requestStream = webRequest.EndGetRequestStream(asynchronousResult);
    requestStream.Close();
    webRequest.BeginGetResponse(new AsyncCallback(ResponseReady), requestStates);
}
void ResponseReady(IAsyncResult asyncResult)
{
    var requestStates = (RequestStates)asyncResult.AsyncState;
    HttpWebRequest webRequest = requestStates.CurrentWebRequest;
    var userFile = requestStates.CurrentUserFile;
    var webResponse = (HttpWebResponse)webRequest.EndGetResponse(asyncResult);
    var reader = new StreamReader(webResponse.GetResponseStream());
    //获取Httphandler类返回的数据
    string responsestring = reader.ReadToEnd();
    reader.Close();
    decimal maxSize = Convert.ToDecimal(responsestring);
    //Check for the file size limit (configurable)
    if (maxSize == 0 || (userFile.FileStream.Length / 1024) <= maxSize)
    {
        this.Dispatcher.BeginInvoke(
            () => _files.Add(userFile)
            );

    }
    else if (maxSize < 0)
    {
        this.Dispatcher.BeginInvoke(
            delegate()
            {
                var messageWindow = new MessageChildWindow
                                                       {
                                                           Message =
                                                               string.Format("不允许上传{0}类文件！",
                                                                             Path.GetExtension(userFile.FileName))
                                                       };
                messageWindow.Show();

                if (MaximumFileSizeReached != null)
                    MaximumFileSizeReached(this, null);
            });
    }
    else
    {
        this.Dispatcher.BeginInvoke(
            () =>
            {
                var messageWindow = new MessageChildWindow
                                        {
                                            Message =
                                                string.Format("{0}{1}{2}KB.",
                                                              Path.GetExtension(userFile.FileName),
                                                              UserMessages.MaxFileSize, (maxSize).ToString())
                                        };
                messageWindow.Show();

                if (MaximumFileSizeReached != null)
                    MaximumFileSizeReached(this, null);
            });
    }
}

效果图片