TaskCanceledException thrown on retrieving a MemoryStream with NPOI workbook - excel

Question

When I hit this API, a TaskCanceledException is thrown with an unhelpful stack trace. I'm using this library: https://npoi.codeplex.com/
public class TestController : ApiController
{
[HttpGet]
public HttpResponseMessage Test()
{
var templateWorkbook = new XSSFWorkbook();
var sheet = templateWorkbook.CreateSheet("TestSheet");
IRow dataRow = sheet.CreateRow(4);
var cell = dataRow.CreateCell(0);
cell.SetCellValue(77);
Stream memoryStream = new MemoryStream();
templateWorkbook.Write(memoryStream);
var httpResponseMessage = new HttpResponseMessage(HttpStatusCode.OK)
{
Content = new StreamContent(memoryStream)
};
httpResponseMessage.Content.Headers.ContentType = new MediaTypeHeaderValue("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
httpResponseMessage.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment") { FileName = "test.xlsx" };
return httpResponseMessage;
}
}
What am I doing wrong? This is my stack trace:
[TaskCanceledException: A task was canceled.]
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +165
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58
System.Web.Http.Owin.d__20.MoveNext() +666
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +137
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58
System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd(Task task) +25
System.Web.Http.Owin.d__0.MoveNext() +1814
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +137
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.d__5.MoveNext()
+187 System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +99
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58
Microsoft.Owin.Security.Infrastructure.d__0.MoveNext() +561
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +137
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58
Microsoft.Owin.Security.Infrastructure.d__0.MoveNext() +561
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +137
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58 Microsoft.Owin.Cors.d__0.MoveNext() +856
System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +137
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.d__5.MoveNext()
+187 System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task
task) +99
System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task
task) +58
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.d__2.MoveNext()
+185 Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.StageAsyncResult.End(IAsyncResult
ar) +69
Microsoft.Owin.Host.SystemWeb.IntegratedPipeline.IntegratedPipelineContext.EndFinalWork(IAsyncResult
ar) +64
System.Web.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
+380 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

Answer 1

I found a solution.
Copying the memory stream to another one and resetting the seek position to 0 seems to fix it:
MemoryStream memoryStream = new MemoryStream();
templateWorkbook.Write(memoryStream);
MemoryStream copy = new MemoryStream(memoryStream.ToArray());
copy.Seek(0, SeekOrigin.Begin);
Seems like a bug in the NPOI library to me...