System.ObjectDisposedException: 无法访问已处置的对象 asp.net-core-webapi

Question

我正在使用 asp.net-core-webapi 并且我也在使用 iTextSharp 在内存流中创建 pdf。

[Route("preview/{Id}")]
        [System.Web.Http.HttpGet]
        public async Task<IActionResult> PreviewSpecSheet(int Id)
        {
            
            FileStreamResult fsr;

            Document document = new Document(PageSize.A4, 25, 25, 30, 30);
            using (MemoryStream ms = new MemoryStream())
            {

                using (PdfWriter writer = PdfWriter.GetInstance(document, ms))
                {



                    //PdfWriter writer = PdfWriter.GetInstance(document, ms);
                    document.Open();
                    //header Image 
                    iTextSharp.text.Image headerImg = iTextSharp.text.Image.GetInstance("D:\go2\Pixelle\specsheet\pixservice\assets\header.jpg");
                    headerImg.SetAbsolutePosition(0, 750);
                    headerImg.ScaleAbsolute(500f, 100.00f);
                    document.Add(headerImg);                    

                    fsr = File(ms, "application/pdf", "test.pdf");
                    return fsr;
                }
                 
            }
           
        }

我收到以下错误：

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'Cannot access a closed file.'.
   at System.IO.FileStream.BeginRead(Byte[] array, Int32 offset, Int32 numBytes, AsyncCallback callback, Object state)
   at System.IO.Stream.<>c.<BeginEndReadAsync>b__48_0(Stream stream, ReadWriteParameters args, AsyncCallback callback, Object state)
   at System.Threading.Tasks.TaskFactory`1.FromAsyncTrim[TInstance,TArgs](TInstance thisRef, TArgs args, Func`5 beginMethod, Func`3 endMethod)
   at System.IO.Stream.BeginEndReadAsync(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.FileStream.ReadAsync(Byte[] buffer, Int32 offset, Int32 count, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Http.StreamCopyOperationInternal.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.Infrastructure.ResourceInvoker.<InvokeResultAsync>g__Logged|21_0(ResourceInvoker invoker, IActionResult result)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResultFilterAsync>g__Awaited|29_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
--- End of stack trace from previous location where exception was thrown ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|19_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)

应用评论解决方案后编辑：

如果我删除使用它工作正常但是当我使用

document.Close();
writer.Close();

在 fsr = File(ms, "application/pdf", "test.pdf"); 之前再次出现同样的错误，如果我不关闭文档和编写器，下载的 pdf 格式已损坏，无法打开。

Answer 1

好的，所以我能够弄清楚这是什么问题。

在原始代码中问题是使用 block ，正如评论部分中已经提到的那样。

但是当我删除 using 时，当我关闭文档和 writer 时仍然面临流关闭的问题。

原因是The PdfWriter class may be closing your stream. Make sure to set the CloseStream property to false.

所以我将 writer CloseStream 属性设置为 false ，就在 declare 之后。

PdfWriter writer = PdfWriter.GetInstance(document, ms);
 writer.CloseStream = false;

并且成功了。

[Route("preview/{Id}")]
        [System.Web.Http.HttpGet]
        public async Task<IActionResult> PreviewSpecSheet(int Id)
        {
            
            FileStreamResult fsr;

            Document document = new Document(PageSize.A4, 25, 25, 30, 30);
            MemoryStream ms = new MemoryStream();


            PdfWriter writer = PdfWriter.GetInstance(document, ms);
            writer.CloseStream = false;



            
            document.Open();
            //header Image 
            iTextSharp.text.Image headerImg = iTextSharp.text.Image.GetInstance("D:\go2\Pixelle\specsheet\pixservice\assets\header.jpg");
            headerImg.SetAbsolutePosition(0, 750);
            headerImg.ScaleAbsolute(500f, 100.00f);
            document.Add(headerImg);

            

            document.Close();
            writer.Close();
            ms.Position = 0;
            fsr = File(ms, "application/pdf", "test.pdf");

            return fsr;
        }

System.ObjectDisposedException: 无法访问已处置的对象 asp.net-core-webapi

System.ObjectDisposedException: Cannot access a disposed object asp.net-core-webapi

asp.net-core

asp.net-core-webapi