I am developing a process to take input from a database object and convert the data to an Excel file export. I am using NPOI tool to do this.

The conversion process works fine, whereas it is a bit lengthy process.

The problem is when one Excel file is processed, if another request is initiated. The first process breaks and the process continues on the new request.

I want to make sure the first process finishes, before the next one can start.

Hence converted the code to below using async await. Please note I am a beginner in this and not completely sure if what I did assures an await for each process. Please correct me if I am wrong.

byte[] IExportTranslator.CreateExcelExportFile(CalSetupVM calSetupVM, ExportCriteriaVM exportCriteriaVM, string name)
{
    return Task.Run(async () => await CreateAsynExportFile(calendarSetupVM, ganttExportCriteriaVM, filterName)).Result;  
}        

public async Task<byte[]> CreateAsynExportFile(CalSetupVM calSetupVM, ExportCriteriaVM exportCriteriaVM, string name)
{
    return await Task.Run(() => doSomeWork(calSetupVM, exportCriteriaVM, name));            
}

private byte[] doSomeWork(CalSetupVM calSetupVM, ExportCriteriaVM exportCriteriaVM, string name)
{
    // do something...
    return byte[...];
}

I did the above code based on some suggestions in the forums. And what I have read around async/await.

The basis need on the process is to wait until doSomeWork is completed and returned the data to be sent to UI and then start any other request which may be initiated during the first run. And so on to queue the request and handle one after the other.

I am developing a process in MVC to take input from a database object and convert the data to an Excel file export. I am using NPOI tool to do this.

The current conversion process is made completely independent with no external dependencies Or Shared objects.

The excel generation works fine and generates the output as required.

The problem arises when the user initiates a second request when the first one is on progress.

When there are more than one requests the process generates the byte[] and returns to the controller to send the file to client side. But on return the file does not download. It only downloads the file related to the last request.

For example:

• when there are 3 requests initiated one after the other.
• The processes is carried out for first
• The processes is carried out for second request
• The processes is carried out for Third request
• All requests are carried out simultaneously
• Finishes Request1, Returns to the controller with Result for Request1
• Does not download the file for Request1
• Finishes Request2, Returns to the controller with Result for Request2
• Does not download the file for Request2
• Finishes Request3, Returns to the controller with Result for Request3
• DOWNLOAD's the file for Request3

How can I handle this and makes sure all generated files are downloaded as they are processed.

**Controller**
public ActionResult ExportExcel(ExportCriteriaVM exportCriteriaVM)
{
.....

    var excelByteArray = _translator.CreateExcelExportFile(..., ..., ...);
 
    return File(excelByteArray, _documentManager.GetMimeType("xlsx"), xlsxName);
}

**Translator**

byte[] IExportTranslator.CreateExcelExportFile(Param1, Param2, Param3)
{
    return doSomeWork(Param1, Param2, Param3);           
}

private byte[] doSomeWork(CalendarSetupVM calendarSetupVM, GanttExportCriteriaVM ganttExportCriteriaVM, string filterName)
{
     using (var ms = new MemoryStream())
     {
     ........
     ........
     return ms.ToArray();
     }
}

How can I ensure the file is downloaded for each request.