C# 如何重用从WebClient.OpenRead（URL）返回的流

我正在为我的团队开发一个简单的实用程序，用于从URL下载图像并将其推送到azure存储blob。我让它工作得很好，但是如果我尝试推送多个blob，第二次和第三次推送只会推送一个空图像。它使其成为blob，但图像长度为0字节。 我得到的流数据如下所示：

private Stream GetImageStream(string imageName)
{
         url = "http://example.com/imageIwantToDownload.jpg"
         WebClient webClient = new WebClient();
         webClient.Headers.Add("Authorization", "Bearer " + token);
         var stream = webClient.OpenRead(new Uri(url));
         if (stream != null)
         {
             stream.ReadTimeout = 500000;
             return stream;
         }    
}

List<string> connectionStringList = new List<string>
{
    ConfigurationManager.AppSettings.Get("UT_CDN_CONNECTION_STRING"),
    ConfigurationManager.AppSettings.Get("QA_CDN_CONNECTION_STRING"),
    ConfigurationManager.AppSettings.Get("PROD_CDN_CONNECTION_STRING")
};

foreach (var connectionString in connectionStringList)
{
      CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connectionString);
      CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
      CloudBlobContainer containerClient = blobClient.GetContainerReference("v1.0/images");
      CloudBlockBlob cloudBlockBlob = containerClient.GetBlockBlobReference(imageName);
      cloudBlockBlob.UploadFromStream(imageStream);         
 }

然后，要推送到blob存储，我正在使用Microsoft.WindowsAzure.storage（由于使用.net 461），并执行以下操作：

private Stream GetImageStream(string imageName)
{
         url = "http://example.com/imageIwantToDownload.jpg"
         WebClient webClient = new WebClient();
         webClient.Headers.Add("Authorization", "Bearer " + token);
         var stream = webClient.OpenRead(new Uri(url));
         if (stream != null)
         {
             stream.ReadTimeout = 500000;
             return stream;
         }    
}

List<string> connectionStringList = new List<string>
{
    ConfigurationManager.AppSettings.Get("UT_CDN_CONNECTION_STRING"),
    ConfigurationManager.AppSettings.Get("QA_CDN_CONNECTION_STRING"),
    ConfigurationManager.AppSettings.Get("PROD_CDN_CONNECTION_STRING")
};

foreach (var connectionString in connectionStringList)
{
      CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connectionString);
      CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
      CloudBlobContainer containerClient = blobClient.GetContainerReference("v1.0/images");
      CloudBlockBlob cloudBlockBlob = containerClient.GetBlockBlobReference(imageName);
      cloudBlockBlob.UploadFromStream(imageStream);         
 }

但是我得到了一个错误，流不允许我去寻找。 我可以只做相同的webClient.OpenRead三次，然后在循环中读取相同的图像三次。但是有没有一种方法可以让我重用我已经拥有的流呢

---

谢谢

您可以参考以下代码，只需使用

imageStream.Position=0：

foreach (var connectionString in connectionStringList)
{
      CloudStorageAccount storageAccount = CloudStorageAccount.Parse(connectionString);
      CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
      CloudBlobContainer containerClient = blobClient.GetContainerReference("v1.0/images");
      CloudBlockBlob cloudBlockBlob = containerClient.GetBlockBlobReference(imageName);
      cloudBlockBlob.UploadFromStream(imageStream);   
      imageStream.Position = 0;      
 }

我做了一些测试，效果很好。
所以当我尝试这个方法时，正如我在帖子中提到的，我得到了一个错误：这个流不支持seek操作。可能是因为我正在将CloudBlobContainer传递到一个方法中？可能是通过引用传递的？当我添加
imageStream.SetLength（0）时，它确实给出了一个错误，但只添加了
imageStream.Position=0，对我来说真的很有效。对我来说不是这样的！我的流是System.IO.stream类型。从System.Net.WebClient-.Net 461OK将流更改为内存流似乎可行：byte[]data=WebClient.DownloadData（新Uri（URL））；返回新的内存流（数据）；