System.IO.File.Copy Throws IOException - file

Question

I am trying to copy some files:
private void DoCopy() {
string[] files = Directory.GetFiles(Application.StartupPath + "\\App_Data", "*.*", SearchOption.AllDirectories);
string sFtpToReadFileFrom = "ftp://<user>:<pass>#mysite.tk/updates/App_Data/";
string sPathToWriteFileTo = Application.StartupPath + "\\App_Data";
WebClient webClient = new WebClient();
webClient.Credentials = new NetworkCredential("user", "pass");
foreach (string s in files)
{
string fileName = Path.GetFileName(s);
string destFile = Path.Combine(sPathToWriteFileTo, fileName);
byte[] fileData = webClient.DownloadData(sFtpToReadFileFrom + fileName); //shows correct bytes
File.Copy(s, destFile, true);
}
}
The exact error is: The process cannot access the file 'C:\AppLauncher\AppLauncher\bin\Debug\App_Data\firstFile' because it is being used by another process.
I followed the 'MSDN How To' here: http://msdn.microsoft.com/en-us/library/cc148994.aspx
If anyone finds any immediate red flags please do let me know.

Answer 1

This is how I see it:
You want to download a file from an FTP server and write it to your local disk.
What you are doing is taking files in your source-directory as targets, which won't work at all. If the files already exist there, which they do if you can acquire their file names there. (hence the exception)
Here is what you must do
Connect to the FTP, acquire the files there (their bytes) and then create files on the disk.
private void DoCopy() {
//string[] files = Directory.GetFiles(Application.StartupPath + "\\App_Data", "*.*", SearchOption.AllDirectories);
//Acquire filenames from FTP-Server instead of local disk!
string sFtpToReadFileFrom = "ftp://<user>:<pass>#mysite.tk/updates/App_Data/";
string sPathToWriteFileTo = Application.StartupPath + "\\App_Data";
WebClient webClient = new WebClient();
webClient.Credentials = new NetworkCredential("user", "pass");
foreach (string s in files)
{
string fileName = Path.GetFileName(s); //create file names based on FTP-server
string destFile = Path.Combine(sPathToWriteFileTo, fileName);
byte[] fileData = webClient.DownloadData(sFtpToReadFileFrom + fileName); //shows correct bytes
//File.Copy(s, destFile, true); Rather use File.WriteAllBytes
File.WriteAllBytes(destFile, fileData);
}
}
See here for an example of File.WriteAllBytes.
The acquiring of the filenames from FTP is not that straightforward, though. There is the FtpWebRequest-class to support you.