C # Web Api - loading and reading data from excel file without saving the file

I have a WebApi that will receive an excel file uploaded by the user as multipart / form-data. I need to read the contents of this file in order to update the database. I was thinking about using EPPlus, but I cannot access the file. Here is the code

public class MyController : APIController
{
    [Route("import")]
    [HttpPost]
    public async Task<HttpResponseMessage> importFile()
    {
        if (!Request.Content.IsMimeMultipartContent())
            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "ERROR");

        Stream stream = await Request.Content.ReadAsStreamAsync();

        var excel = new ExcelPackage(stream);
        var workbook = excel.Workbook;

        var sheet = excel.Workbook.Worksheets.First();

        ...

}

      

        
        
        
      

    

The error is listed var sheet = excel.Workbook.Worksheets.First()

as there is no worksheet in the workbook (but the physical file has 2).

What am I doing wrong? Is it a flow?

I'm trying to have a separate library for each type of Excel file (.xls or .xlsx), but I can't seem to make it work with .xls files. I am using ExcelDataReader and now the code looks like this:

public async Task<HttpResponseMessage> importFile()
    {
        if (!Request.Content.IsMimeMultipartContent())
            return Request.CreateErrorResponse(HttpStatusCode.BadRequest, "NOT MULTIPART");

        Stream stream = await Request.Content.ReadAsStreamAsync();

        //open xlsx file            
        var excel = new ExcelPackage(stream);
        var workbook = excel.Workbook;
        try
        { 
            var sheet = excel.Workbook.Worksheets.First();

            //working fine with EPPlus for .xlsx files 
            return Request.CreateResponse(HttpStatusCode.OK, errors);                

        }catch(Exception)//open xls file
        {  
           //if its a .xls file it will throw an Exception              
        }

        //using ExcelDataReader to open .xls file
        IExcelDataReader excelReader = ExcelReaderFactory.CreateBinaryReader(stream);
        DataSet result = excelReader.AsDataSet();

        // the DataSet is null, stream is setted as ReadOnlyStream and stream.length is throwing an ObjectDisposedException
        return Request.CreateErrorResponse(HttpStatusCode.InternalServerError, "erro");            
    }