silverlight example code uploaded with webclient large file

Client:

     /// <summary> 
     ///  Writes data to the stream  
     /// </summary> 
     /// <param name="url"></param> 
     /// <param name="callback"></param> 
     public async static Task<bool> Write(string url, Stream clientStream) 
     { 
         if (clientStream.Length > 25*1024*1024) 
             url += "&t=1"; //  Means to upload a large file 
         try 
         { 
             Up(url, clientStream);
             return true; 
         } 
         catch { }
         return false; 
     }
     public async static Task Up(string url, Stream sourceStream) 
     { 
         var wc = new WebClient();
         byte[] buffer = new byte[25*1024*1024]; 
         int bufLen = sourceStream.Read(buffer, 0, buffer.Length); 
         if (bufLen < 1) 
         { 
             sourceStream.Close(); 
             return; 
         } 
        wc.WriteStreamClosed += (s, e) => 
         { 
             if (sourceStream.CanRead) 
                 Up(url, sourceStream); 
             else 
                 sourceStream.Close(); 
         }; 
         var serverStream = await wc.OpenWriteTaskAsync(url, "POST"); 
         serverStream.Write(buffer, 0, bufLen);
         serverStream.Close(); 
     }

Server:

private void Save() 
       { 
           string data = Context.Request.QueryString["data"].Base64StringDecode("ABC"); 
           if (data.IsNullOrEmpty()) 
               return;
           var m = JsonConvert.DeserializeObject<FileUploadModel>(data); 
           if (m == null) 
               return;
           var isSplitBlock = Context.Request.QueryString["t"]=="1";   // Whether to block upload 
           #region  Save the file 
           //  Initialization directory  
           string dirPath = Path.Combine(ConfigHelper.UploadPath, m.Dir);   //  File save path  
           if (!Directory.Exists(dirPath)) 
               Directory.CreateDirectory(dirPath);
           //  Address of the file  
           string filePath = Path.Combine(dirPath, m.FileName); 
           if (!isSplitBlock) 
           { 
               if (File.Exists(filePath)) 
                   File.Delete(filePath); 
           }
           int bufLen = 0; 
           byte[] buffer = new byte[4096]; 
           using (FileStream fs = new FileStream(filePath, FileMode.OpenOrCreate, FileAccess.ReadWrite)) 
           { 
               fs.Seek(0, SeekOrigin.End);
               //  Write to the original file  
               Stream sr = Context.Request.InputStream;
               while ((bufLen = sr.Read(buffer, 0, buffer.Length)) > 0) 
                   fs.Write(buffer, 0, bufLen);
               sr.Close(); 
               sr.Dispose();
               //  The thumbnail  
               try 
               { 
                   if (!m.NeedThumbnail) 
                       return;
                   dirPath = Path.Combine(dirPath, "Small"); 
                   if (!Directory.Exists(dirPath)) 
                       Directory.CreateDirectory(dirPath);
                   filePath = Path.Combine(dirPath, m.FileName); 
                   if (File.Exists(filePath)) 
                       File.Delete(filePath);
                   using (var pic = GetThumbnail(fs, 300, 300)) 
                   { 
                       pic.Save(filePath); 
                   } 
               } 
               catch { } 
           }
           #endregion
           #region  Delete the original file 
           //  Delete the original file 
           if (m.OldFilePath.IsNullOrEmpty()) 
           { 
               return; 
           }
           try 
           { 
               filePath = Path.Combine(ConfigHelper.UploadPath, m.OldFilePath); 
               if (File.Exists(filePath)) 
                   File.Delete(filePath);
               if (m.NeedThumbnail) 
               { 
                   filePath = Path.Combine(ConfigHelper.UploadPath, m.OldThumbnailImagePath); 
                   if (File.Exists(filePath)) 
                       File.Delete(filePath); 
               } 
           } 
           catch (Exception ex) 
           {
           }
           #endregion 
       } 

Note: After each stream is saved, read the data in the next block; otherwise, the block flow data before the first block will be overwritten by the block flow data after the first block.
Focus on the results as well as the process