C#中从服务器向客户端传输.dotx文件时的数据丢失问题

我将文件存储在Azure Blob Storage中，通过ASP.NET实现下载功能，点击按钮触发以下代码调用中间服务获取文件：

protected async void WebPagePopupDownloadDocumentButtonOnClick(object sender, EventArgs e)
{
    string rawJson = JsonResultHiddenField.Value;

    string unescapedJson = System.Web.HttpUtility.HtmlDecode(rawJson).Trim('"');

    if (unescapedJson.StartsWith("\"") && unescapedJson.EndsWith("\""))
    {
        unescapedJson = unescapedJson.Substring(1, unescapedJson.Length - 2);
    }

    unescapedJson = unescapedJson.Replace("\\\"", "\"");

    unescapedJson = unescapedJson.Replace("\\r", "").Replace("\\n", "");

    try
    {
        var jsonObject = JObject.Parse(unescapedJson);
        string fileUrl = (string)jsonObject["Documents"]?[0]?["FileUrl"];
        if (fileUrl != null)
        {
            using (var httpClient = new HttpClient())
            {
                string guidText = GuidLabel.Text;
                string guid = guidText.Substring(guidText.IndexOf(":") + 2).Trim();
                var configManager = Container.Resolve<IFeConfigManager>();
                var nawServicesUrl = configManager.GetModel<KeyValueConfig>(ConfigurationModels.SendToInfolex, ApplicationManager.Instance.RecoverProductId())["NawServicesUrl"];

                var accessToken = SessionManager.Instance.RecoverSession()?.OidcWorkflowData?.TokenResponseData?.AccessToken;
                httpClient.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", accessToken);

                string fileName = Path.GetFileName(fileUrl);
                string url = $"{nawServicesUrl}{DOWNLOAD_DOCUMENT_OP}?guid={guid}&fileName={fileName}";

                var response = await httpClient.GetAsync(url);
                response.EnsureSuccessStatusCode();

                var fileBytes = await response.Content.ReadAsByteArrayAsync();

                string tempFilePath = Path.Combine(Path.GetTempPath(), fileName);
                File.WriteAllBytes(tempFilePath, fileBytes);

                Response.Clear();
                Response.ContentType = GetContentType(fileName);
                Response.AddHeader("Content-Disposition", $"attachment; filename={fileName}");
                Response.TransmitFile(tempFilePath);
                Response.End();
            }
        }
        else
        {
            Console.WriteLine("No FileUrl found.");
        }
    }
    catch (JsonReaderException ex)
    {
        Console.WriteLine($"JSON parse error: {ex.Message}");

    }

}

private string GetContentType(string fileName)
{
    string extension = Path.GetExtension(fileName).ToLower();
    switch (extension)
    {
        case ".pdf":
            return "application/pdf";
        case ".doc":
            return "application/msword";
        case ".docx":
            return "application/vnd.openxmlformats-officedocument.wordprocessingml.document";
        case ".html":
            return "text/html";
        case ".dotx":
            return "application/vnd.openxmlformats-officedocument.wordprocessingml.template";
        default:
            return "application/octet-stream";

    }
}

问题现象 #

目前HTML、PDF文件下载后可正常打开，但Office文档出现异常：

• .docx文件打开时，Microsoft Word提示存在不可读内容，确认后可打开；
• .dotx文件直接无法打开。

直接从Azure Blob Storage下载的文件可正常打开，对比发现通过应用下载的文件大小更小，用HxD工具查看后确认缺失了最后10KB数据。

已尝试的解决方案 #

我试过几种方案但都未解决问题：

1. 先将文件下载到服务器临时路径再传输（即上述原始代码逻辑）
2. 直接传输字节数组：

var fileBytes = await response.Content.ReadAsByteArrayAsync();  
Response.Clear(); 
Response.ContentType = GetContentType(fileName); 
Response.AddHeader("Content-Disposition", $"attachment; filename={fileName}"); 
Response.BinaryWrite(fileBytes); 
Response.End();     

3. 异步写入临时文件：

var fileBytes = await response.Content.ReadAsByteArrayAsync();

string tempFilePath = Path.Combine(Path.GetTempPath(), fileName);
await WriteBytesAsync(tempFilePath, fileBytes);

...

private async Task WriteBytesAsync(string filePath, byte[] bytes)
 {
     using (var fileStream = new FileStream(filePath, FileMode.Create, FileAccess.Write, FileShare.None, bufferSize: 4096, useAsync: true))
     {
         await fileStream.WriteAsync(bytes, 0, bytes.Length);
     }
}

内容的提问来源于stack exchange，提问作者Julio Escudero Cuesta