Server.map path not working in asp.net - asp.net

Question

I am using this code to download a excel file which exist in my solution. I have added a folder FileUpload and added a excel file UploadCWF.xlsx. My code is workin in local host. But not working when I host this to server.I am getting error - Could not find a part of the path. My code -
string filePath = HttpContext.Current.Server.MapPath("~/FileUpload/");
string _DownloadableProductFileName = "UploadCWF.xlsx";
System.IO.FileInfo FileName = new System.IO.FileInfo(filePath + "\\" + _DownloadableProductFileName);
FileStream myFile = new FileStream(filePath + "\\" + _DownloadableProductFileName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
//Reads file as binary values
BinaryReader _BinaryReader = new BinaryReader(myFile);
//Check whether file exists in specified location
if (FileName.Exists)
{
try
{
long startBytes = 0;
string lastUpdateTiemStamp = File.GetLastWriteTimeUtc(filePath).ToString("r");
string _EncodedData = HttpUtility.UrlEncode(_DownloadableProductFileName, Encoding.UTF8) + lastUpdateTiemStamp;
Response.Clear();
Response.Buffer = false;
Response.AddHeader("Accept-Ranges", "bytes");
Response.AppendHeader("ETag", "\"" + _EncodedData + "\"");
Response.AppendHeader("Last-Modified", lastUpdateTiemStamp);
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment;filename=" + FileName.Name);
Response.AddHeader("Content-Length", (FileName.Length - startBytes).ToString());
Response.AddHeader("Connection", "Keep-Alive");
Response.ContentEncoding = Encoding.UTF8;
//Send data
_BinaryReader.BaseStream.Seek(startBytes, SeekOrigin.Begin);
//Dividing the data in 1024 bytes package
int maxCount = (int)Math.Ceiling((FileName.Length - startBytes + 0.0) / 1024);
//Download in block of 1024 bytes
int i;
for (i = 0; i < maxCount && Response.IsClientConnected; i++)
{
Response.BinaryWrite(_BinaryReader.ReadBytes(1024));
Response.Flush();
}
}
catch (Exception es)
{
throw es;
}
finally
{
Response.End();
_BinaryReader.Close();
myFile.Close();
}
}
else
System.Web.UI.ScriptManager.RegisterStartupScript(this, GetType(),
"FileNotFoundWarning", "alert('File is not available now!')", true);
Please some one help me.

Answer 1

You should first concat filepath and filename then get path using server.mappath.
You should write code like this
string filePath = HttpContext.Current.Server.MapPath("~/FileUpload/UploadCWF.xlsx");
System.IO.FileInfo FileName = new System.IO.FileInfo(filePath);