How to rewrite Web Api with best practice and best performance?

ahmed salah 3,216 Reputation points

I work on core 2.2 web API using C# language

I need to rewrite function below with best syntax and with best practice

web API below get Excel file from upload and return Excel file

it working without any issue but I need to rewrite it with best syntax and practice

some points I need to changes :

concatenate path is best thing using

are streaming using correctly

are memory copying file is correct

[HttpPost, DisableRequestSizeLimit]
    public IActionResult Upload()
            var DisplayFileName = Request.Form.Files[0];
            string fileName = DisplayFileName.FileName.Replace(".xlsx", "-") + Guid.NewGuid().ToString() + ".xlsx";
            string Month = DateTime.Now.Month.ToString();
            string DirectoryCreate = myValue1 + "\\" + Month + "\\" + fileName;
            string exportDirectory = myValue2 + "\\" + Month;
            string exportPath = myValue2 + "\\" + Month + "\\" + fileName;
            string FinalPath = exportPath;

            if (!Directory.Exists(DirectoryCreate))

            if (!Directory.Exists(exportDirectory))

            CExcel ex = new CExcel();
            if (DisplayFileName.Length > 0)
                var filedata = ContentDispositionHeaderValue.Parse(Request.Form.Files[0].ContentDisposition).FileName.Trim('"');
                var dbPath = Path.Combine(DirectoryCreate, fileName);

                using (var stream = new FileStream(dbPath, FileMode.Create))
                string error = "";
                int rowCount = 0;
                string inputTemplatePath = "";

                var InputfilePath = System.IO.Path.Combine(GetFilesDownload, "DeliveryGeneration_Input.xlsx");
                bool areIdentical = ex.CompareExcel(dbPath, InputfilePath, out rowCount, out error);
                if (areIdentical == true)
                    List<InputExcel> inputexcellist = new List<InputExcel>();
                    inputexcellist = ex.Import(dbPath);
                    List<string> mods = new List<string>();
                    mods = inputexcellist.Select(x => x.ModuleName).Distinct().ToList();
                    var OutputfilePath = System.IO.Path.Combine(GetFilesDownload, "DeliveryGeneration_Output.xlsx");
                    if (System.IO.Directory.Exists(Path.Combine(exportDirectory, fileName)))
                        throw new Exception("Ok so the error message IS right.");
                    System.IO.File.Copy(OutputfilePath, Path.Combine(exportDirectory, fileName), true);

                    SqlConnection con;
                    foreach (var m in mods)
                        List<InputExcel> inputmodulelist = new List<InputExcel>();
                        inputmodulelist = inputexcellist.Where(x => x.ModuleName == m).ToList();
                        var dtimport = DatatableConversion.ToDataTable(inputmodulelist);
                        DataTable dtexport = new DataTable();
                        dtexport = _deliveryService.LoadExcelToDataTable(_connectionString, dtimport);
                        ex.Export(dtexport, m, exportPath);

                var memory2 = new MemoryStream();
                using (var stream = new FileStream(exportPath, FileMode.Open))
                memory2.Position = 0;

                return File(memory2, "text/plain", Path.GetFileName(exportPath));

                return BadRequest();
        catch (Exception ex)
            return StatusCode(500, $"Internal server error: {ex}");
A set of technologies in the .NET Framework for building web applications and XML web services.
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A set of technologies in the .NET Framework for building web applications and XML web services.
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An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
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2 answers

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  1. Bruce ( 59,021 Reputation points

    You should be using async file and database calls, or you will limit scaling.

    It also looks like you write a file, then read it back. And why the extra memory copy?

  2. Zhi Lv - MSFT 32,051 Reputation points Microsoft Vendor

    Hi @ahmed salah ,

    can you please see me how to use async task on web api above

    To convert the Upload method to the async method, you can refer the following sample:

    in the service methods: from your code, since you are using _deliveryService to call the database, you can change the code as below:

    public interface IDeliveryService  
        Task<string> LoadExcelToDataTableAsync(string connectionstring, string inport);  
    public class DeliveryService : IDeliveryService  
        private readonly ApplicationDbContext _context;  
        public DeliveryService(ApplicationDbContext context)  
            _context = context;  
        public async Task<string> LoadExcelToDataTableAsync(string connectionstring, string inport)  
            // do something  
            //access the database via _context.  
            return await Task.FromResult<string>("OK");  

    In the above code, I access the database via EF code, more detail you can refer this article.

    Then, in the controller, the code as below:

        private readonly IDeliveryService _deliveryService;  
        public HomeController(IDeliveryService deliveryService)  
            _deliveryService = deliveryService;  
        public async Task<IActionResult> UploadAsync()  
            var result = await _deliveryService.LoadExcelToDataTableAsync("connection", "inport");  
            return View();  

    More detail information about asynchronous programming, see Asynchronous programming with async and await.

    Besides, here is an article about ASP.NET Core Performance Best Practices, you can refer it.

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    Best regards,