将字节数组写入C＃中的独立存储区文件Windows Phone 7应用程序无效

Question

我有一个C＃Windows Phone 7.1应用程序，它从外部Web服务器下载PDF文件，然后（尝试）将其保存到独立存储区作为一个文件。我已经尝试了几种不同的方法来完成这个工作，但是文件总是会大大超过30％，而当我在文本编辑器中打开文件时，文件开始时会看到USUAL'PDF'字符，然后是编码的字符，我基本上看到垃圾。我使用的测试文件应该是161k，但是当我用Isolated Storage Explorer查看文件时，它是271k。

首先我将文件下载到一个字符串。我在调试器的这一点检查了字符串，它确实包含了正确的值，并且它是正确的长度。当我尝试将它写入隔离的存储区域时发生问题。我试过StreamWriter & BinaryWriter具有相同的无效结果。生成的文件的内容似乎是一长串垃圾字符。请注意，如果文件存在以防万一，在写出内容之前，我正在删除该文件。以下是我使用BinaryWriter版本的代码。哪里不对？

async public static Task URLToFileAsync(
           string strUrl, 
           string strDestFilename, 
           IProgress<int> progress, 
           CancellationToken cancelToken) 
{ 
    strUrl = strUrl.Trim(); 

    if (String.IsNullOrWhiteSpace(strUrl)) 
     throw new ArgumentException("(Misc::URLToFileAsync) The URL is empty."); 

    strDestFilename = strDestFilename.Trim(); 

    if (String.IsNullOrWhiteSpace(strDestFilename)) 
     throw new ArgumentException("(Misc::URLToFileAsync) The destination file name is empty."); 

    // Create the isolated storage file. 
    // FileStream fs = Misc.CreateIsolatedStorageFileStream(strDestFilename); 
    IsolatedStorageFile isoStorage = IsolatedStorageFile.GetUserStoreForApplication(); 

    // Delete the file first. 
    if (isoStorage.FileExists(strDestFilename)) 
     isoStorage.DeleteFile(strDestFilename); 

    IsolatedStorageFileStream theIsoStream = isoStorage.OpenFile(strDestFilename, FileMode.Create); 

    FileStream fs = theIsoStream; 

    // If the stream writer is NULL, then the file could not be created. 
    if (fs == null) 
     throw new System.IO.IOException("(Misc::URLToFileAsync) Error creating or writing to the file named: " + strDestFilename); 

    BinaryWriter bw = new BinaryWriter(fs); 

    try 
    { 

     // Call URLToStringAsync() to get the web file as a string first. 
     string strFileContents = await URLToStringAsync(strUrl, progress, cancelToken); 

     // >>>> NOTE: strFileContents looks correct and is the correct size. 

     // Operation cancelled? 
     if (!safeCancellationCheck(cancelToken)) 
     { 
      // Note. BinaryWriter does not have an Async method so we take the hit here 
      // to do a synchronous operation. 
      // See this Stack Overflow post. 
      // http://stackoverflow.com/questions/10315316/asynchronous-binaryreader-and-binarywriter-in-net 

      // >>>> NOTE: strFileContents.ToCharArray() looks correct and is the correct length. 
      bw.Write(strFileContents.ToCharArray(), 0, strFileContents.Length); 
     } // if (safeCancellationCheck(cancelToken)) 
    } 
    finally 
    { 
     // Make sure the file is cleaned up. 
     bw.Flush(); 
     bw.Close(); 

     // Make sure the file is disposed. 
     bw.Dispose(); 
    } // try/finally 

    // >>>> NOTE: output file in Isolated Storage Explorer is the wrong size and contains apparently junk. 
} // async public static void URLToFileAsync 

Answer 1

您无法将二进制文件下载到字符串中。结果将不正确，正如你发现的那样。

看到这个答案，它演示了如何下载二进制文件到独立存储：https://stackoverflow.com/a/6909201/1822514