本地正常服务器报错：Asp.Net读取IFormFile时流复制异常

错误信息 #

{
  "error": "Error while copying content to a stream.",
  "exceptionType": "System.Net.Http.HttpRequestException",
  "innerException": "Cannot access a disposed object.\r\nObject name: 'System.Net.Http.StreamContent'.",
  "stackTrace": "   at System.Net.Http.HttpContent.CheckDisposed()\r\n"
}

代码实现 #

[RequestFormLimits(MultipartBodyLengthLimit = 52428800, ValueLengthLimit = 52428800)]
public async Task<IActionResult> ImportSheet([FromForm] IFormFile uploadedFile)
{
    var isClean = await _antimalwareScanService.PostSingleFileResponseAsync(uploadedFile);
    if (isClean)
    {
        if (uploadedFile is null)
        {
            return BadRequest();
        }
        if (!string.IsNullOrEmpty(uploadedFile.FileName))
        {
            using var stream = uploadedFile.OpenReadStream();
            //using var memoryStream = new MemoryStream();
            //await stream.CopyToAsync(memoryStream);
            using ExcelPackage excel = new(stream);
            ExcelPackage.LicenseContext = LicenseContext.NonCommercial;

            ExcelWorkbook workbook = excel.Workbook;
            ExcelWorksheets worksheets = workbook.Worksheets;
            var psWorksheets = worksheets.FirstOrDefault(x => x.Name.ToLower().Contains("prof services"));
            if (psWorksheets != null)
            {
                await _fileViewModelService.UploadProfServicesFile(psWorksheets);
            }
            stream.Dispose();
        }
    }

    return Ok();
}

问题分析与解决方案 #

1. 手动调用stream.Dispose()是冗余操作：stream通过using声明，会在代码块结束时自动释放资源。提前手动释放会导致后续ExcelPackage内部可能的流访问操作触发已释放对象异常，直接移除该调用即可。

2. 服务器环境下反病毒扫描可能消耗了原文件流：本地环境的扫描逻辑可能未完全读取IFormFile的流，但服务器端扫描服务PostSingleFileResponseAsync可能已经读取并消耗了原流，导致后续打开的流无法正常使用。解决方案是提前将文件内容复制到内存流，避免原流被消耗：

   [RequestFormLimits(MultipartBodyLengthLimit = 52428800, ValueLengthLimit = 52428800)]
   public async Task<IActionResult> ImportSheet([FromForm] IFormFile uploadedFile)
   {
       if (uploadedFile is null || string.IsNullOrEmpty(uploadedFile.FileName))
       {
           return BadRequest();
       }
   
       // 先将文件复制到内存流保存
       using var memoryStream = new MemoryStream();
       await uploadedFile.CopyToAsync(memoryStream);
       memoryStream.Position = 0;
   
       // 创建新的IFormFile用于扫描，避免原流被消耗
       var scannedFile = new FormFile(memoryStream, 0, memoryStream.Length, uploadedFile.Name, uploadedFile.FileName);
       var isClean = await _antimalwareScanService.PostSingleFileResponseAsync(scannedFile);
   
       if (isClean)
       {
           // 重置内存流位置，供ExcelPackage读取
           memoryStream.Position = 0;
           using ExcelPackage excel = new(memoryStream);
           ExcelPackage.LicenseContext = LicenseContext.NonCommercial;
   
           ExcelWorkbook workbook = excel.Workbook;
           ExcelWorksheets worksheets = workbook.Worksheets;
           var psWorksheets = worksheets.FirstOrDefault(x => x.Name.ToLower().Contains("prof services"));
           if (psWorksheets != null)
           {
               await _fileViewModelService.UploadProfServicesFile(psWorksheets);
           }
       }
   
       return Ok();
   }
   

内容的提问来源于stack exchange，提问作者Sabri Baazaoui