I have to set password protection to that folder while creating dynamically

My requirement is in windows desktop application I have to create a folder and download files from database to that folder.I have to set password protection to that folder while creating dynamically.

string[] FileName = lblPath.Split('.');
FullFileName = lbFileName + '.' + FileName[1];
string s =@"C:\SriGayatriLearning\";
// string s22 = @"C:\SriGayatriLearning\";
DirectoryInfo dir = new DirectoryInfo(s);
if (!dir.Exists)
{
Directory.CreateDirectory(s);
}
s = s + FullFileName;
using (WebClient webClient = new WebClient())
{
webClient.DownloadFile(path, s);
}
Process proc = new Process();
proc.StartInfo.FileName = s;
proc.Start();