Cannot use Server.MapPath

Question

you can try using this

    System.Web.HttpContext.Current.Server.MapPath(path);

or use HostingEnvironment.MapPath

    System.Web.Hosting.HostingEnvironment.MapPath(path);

Your project needs to reference assembly System.Web.dll. Server is an object of type HttpServerUtility. Example:

HttpContext.Current.Server.MapPath(path);

System.Web.HttpContext.Current.Server.MapPath("~/") gives null if we call it from a thread.

So, Try to use

System.Web.Hosting.HostingEnvironment.MapPath("~/")

Firt add a reference to System.web, if you don't have. Do that in the References folder.

You can then use Hosting.HostingEnvironment.MapPath(path);

bool IsExist = System.IO.Directory.Exists(HttpContext.Current.Server.MapPath("/UploadedFiles/"));
if (!IsExist)
    System.IO.Directory.CreateDirectory(HttpContext.Current.Server.MapPath("/UploadedFiles/"));

StreamWriter textWriter = File.CreateText(Path.Combine(HttpContext.Current.Server.MapPath("/UploadedFiles/") + "FileName.csv"));
var csvWriter = new CsvWriter(textWriter, System.Globalization.CultureInfo.CurrentCulture);
csvWriter.WriteRecords(classVM);