Setting NTFS Permissions with C# Programmatically

Reference the dll, and use it.

using Microsoft.Win32.Security;

Here's a method to add a dir, and set NTFS permissions on it for a given user:

private Boolean CreateDir(String strSitePath, String strUserName) {
       Boolean bOk;
       try {
              Directory.CreateDirectory(strSitePath);
              SecurityDescriptor secDesc = SecurityDescriptor.GetFileSecurity(strSitePath, SECURITY_INFORMATION.DACL_SECURITY_INFORMATION);
              Dacl dacl = secDesc.Dacl;
              Sid sidUser = new Sid (strUserName);
 
              // allow: folder, subfolder and files
              // modify
              dacl.AddAce (new AceAccessAllowed (sidUser, AccessType.GENERIC_WRITE | AccessType.GENERIC_READ | AccessType.DELETE | AccessType.GENERIC_EXECUTE , AceFlags.OBJECT_INHERIT_ACE | AceFlags.CONTAINER_INHERIT_ACE));
             
              // deny: this folder
              // write attribs
              // write extended attribs
              // delete
              // change permissions
              // take ownership
              DirectoryAccessType DAType = DirectoryAccessType.FILE_WRITE_ATTRIBUTES | DirectoryAccessType.FILE_WRITE_EA | DirectoryAccessType.DELETE | DirectoryAccessType.WRITE_OWNER | DirectoryAccessType.WRITE_DAC;
              AccessType AType = (AccessType)DAType;
              dacl.AddAce (new AceAccessDenied (sidUser, AType));
 
              secDesc.SetDacl(dacl);
              secDesc.SetFileSecurity(strSitePath, SECURITY_INFORMATION.DACL_SECURITY_INFORMATION);
              bOk = true;
       } catch {
              bOk = false;
       }
       return bOk;
} /* CreateDir */

The AceFlags determine the level of inheritance on the object.
And the DirectoryAccessType is used to create a AccessType with some permissions not in the AccessType enum.
I hope this is useful.