Invalid Data Exception when using ExcelDataReader

Question

I have a program that reads Excel file using ExcelDataReader.dll.
Everything was perfect until I moved the file reading to a new task:

Stream output = new MemoryStream();
httpRequest.Files[0].InputStream.CopyToAsync(output);
ImportDataWriter importDatawRiter = new ImportDataWriter(authenticationInfo);
Task.Run(() => importDatawRiter.ImportFile(output));  

ImportLine Code:

public ImportResult ImportFile(Stream fs)
{
        IExcelDataReader reader = ExcelReaderFactory.CreateOpenXmlReader(fs);
}

Now this line:

IExcelDataReader reader = ExcelReaderFactory.CreateOpenXmlReader(fs);

causes an Exception:

An exception of type 'System.IO.InvalidDataException' occurred in System.IO.Compression.dll but was not handled in user code

Message:

End of Central Directory record could not be found.

The Exception occurs from the second time I call the function.

What Can Be The Problem?

Answer 1

The problem is that you are not waiting for the Copy task to finish, so when you get to read the MemoryStream, it is not full (it may even be completely empty), so, change your code to:

Stream output = new MemoryStream();
await httpRequest.Files[0].InputStream.CopyToAsync(output);
^^^^^
ImportDataWriter importDatawRiter = new ImportDataWriter(authenticationInfo);
Task.Run(() => importDatawRiter.ImportFile(output));  

And, unless ImportFile is a fire-and-forget action, I'd suggest you to use

await Task.Run(() => importDatawRiter.ImportFile(output));