在 AWS Lambda 中获取 "The inner stream position has changed unexpectedly"

Question

我正在 ASP.Net 核心实现文件上传。在 Windows 上本地测试时一切正常，但是当我在 AWS Lambda 上部署我的代码时，我得到

"System.InvalidOperationException: The inner stream position has changed unexpectedly. at Microsoft.AspNetCore.Http.Internal.ReferenceReadStream.VerifyPosition() at Microsoft.AspNetCore.Http.Internal.ReferenceReadStream.Read(Byte[] buffer, Int32 offset, Int32 count) at System.IO.Stream.CopyTo(Stream destination, Int32 bufferSize)"

我的代码：

[HttpPost]
[Route("")]
[Authorize]
public IActionResult Store([FromForm] MyFiles files)
{
    var stream1 = files.File1.OpenReadStream();
    var stream2 = files.File2.OpenReadStream();
    string result;
    using (MemoryStream ms = new MemoryStream())
    {
        stream1.CopyTo(ms);
        ms.Position = 0;
        result= GetCrcForFile(ms);
    }
}

public class MyFiles
{
    public IFormFile File1 { get; set; }
    public IFormFile File2 { get; set; }
}

public string GetCrcForFile(Stream result)
{
    uint crc = 0;
    using (MemoryStream ms = new MemoryStream())
    {
        result.CopyTo(ms);
        var bytes = ms.ToArray();
        crc = Crc32Algorithm.Compute(bytes);
        return crc.ToString("X");
    }
}

异常发生在行 result.CopyTo(ms);

我不确定是 .Net Core 在 Linux 环境或 AWS Lambda 问题上表现不同，还是我做错了什么。

Answer 1

如 in this issue 所示，根据您使用的服务器类型，您无法按任意顺序访问文件流。您需要按顺序打开和处理文件，否则您将收到此 "The inner stream position has changed unexpectedly" 异常。

因此，请确保：

在 File1 上调用 OpenReadStream，然后完全处理文件的内容
然后，在 File2 上调用 OpenReadStream，依此类推

在 AWS Lambda 中获取 "The inner stream position has changed unexpectedly"

Getting "The inner stream position has changed unexpectedly" in AWS Lambda

c#

stream

asp.net-core-2.1