asp.net-core - 大文件（> 2 GB）的 ASP.NET 核心中的 FileStreamResult 导致 System.IO.IOException：流太长

Question

我正在尝试使用FileStreamResult-发送一个大文件

return new UnbufferedFileStreamResult(new FileStream(apiResponse.url, FileMode.Open, FileAccess.Read), "text/csv") { FileDownloadName = new FileInfo(apiResponse.url).Name };

是UnbufferedFileStreamResult：

public class UnbufferedFileStreamResult : FileStreamResult {
    public UnbufferedFileStreamResult(Stream fileStream, string contentType) : base(fileStream, contentType) {

    }

    public override void ExecuteResult(ActionContext context) {
        context.HttpContext.DisableOutputBuffering();
        base.ExecuteResult(context);
    }
}

这似乎适用于达到一定大小的文件，但如果它们变得太大，我会得到以下异常：

System.IO.IOException: Stream was too long.
   at System.IO.MemoryStream.Write(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.MemoryStream.WriteAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Http.Extensions.StreamCopyOperation.CopyToAsync(Stream source, Stream destination, Nullable`1 count, Int32 bufferSize, CancellationToken cancel)
   at Microsoft.AspNetCore.Mvc.Infrastructure.FileResultExecutorBase.WriteFileAsync(HttpContext context, Stream fileStream, RangeItemHeaderValue range, Int64 rangeLength)
   at Microsoft.AspNetCore.Mvc.Infrastructure.FileStreamResultExecutor.ExecuteAsync(ActionContext context, FileStreamResult result)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeResultAsync(IActionResult result)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResultFilterAsync[TFilter,TFilterAsync]()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResultExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, O

FileStreamResultExecutorBase因此，在它进入 http 输出流之前，它似乎正在将我的文件流复制到内存流中。我的问题是 1）为什么要这样做，2）我怎样才能防止这种行为，以及 3）是否有这样的结果实现FileStreamResult可以直接从输入流读取到输出流而无需先复制到内存？

标签： asp.net-corefilestreamresult