ACL's

Working with files:

// Our file security object
FileSecurity fs = File.GetAccessControl("c:\\filename.txt", AccessControlSections.All);
 
// Showing access rules data
AuthorizationRuleCollection arc = fs.GetAccessRules(true, true, typeof(NTAccount));
foreach (FileSystemAccessRule ar in arc)
{
    MessageBox.Show("Access to: " + ar.IdentityReference.Value);
    MessageBox.Show("Access to: " + ar.AccessControlType.ToString());
    MessageBox.Show("Access to: " + ar.FileSystemRights.ToString());
}
 
// Showing audit rules data
arc = fs.GetAuditRules(true, true, typeof(NTAccount));
foreach (FileSystemAuditRule ar in arc)
{
    MessageBox.Show("Audit to: " + ar.IdentityReference.Value);
    MessageBox.Show("Audit to: " + ar.AuditFlags.ToString());
    MessageBox.Show("Audit to: " + ar.FileSystemRights.ToString());
}

Working with directories:

// Our file security object
DirectorySecurity ds = Directory.GetAccessControl("c:\\temp");
 
// Showing access rules data
AuthorizationRuleCollection arc = ds.GetAccessRules(true, true, typeof(NTAccount));
foreach (FileSystemAccessRule ar in arc)
{
    MessageBox.Show("Access to: " + ar.IdentityReference.Value);
    MessageBox.Show("Access to: " + ar.AccessControlType.ToString());
    MessageBox.Show("Access to: " + ar.FileSystemRights.ToString());
}

Performing changes in file ACL's:

// Our file security object
FileSecurity fs = File.GetAccessControl("c:\\filename.txt", AccessControlSections.All);
 
// Add a new rule
fs.AddAccessRule(new FileSystemAccessRule("Guests", FileSystemRights.Read, AccessControlType.Allow));
 
// Save changes
File.SetAccessControl("c:\\filename.txt", fs);

For directories:

// Our file security object
DirectorySecurity ds = Directory.GetAccessControl("c:\\temp", AccessControlSections.All);
 
// Add a new rule
ds.AddAccessRule(new FileSystemAccessRule("Guests", FileSystemRights.Read, AccessControlType.Allow));
 
// Save changes
Directory.SetAccessControl("c:\\temp", ds);

Creating directories with initial permissions:

// Our file security object
DirectorySecurity ds = new DirectorySecurity();
 
// Setting the rule
ds.AddAccessRule(new FileSystemAccessRule("Guests", FileSystemRights.FullControl, AccessControlType.Allow));
 
// Creating the directory with our ACL's
Directory.CreateDirectory("c:\\guests", ds);

Removing ACL's:

// Our file security object
FileSecurity fs = File.GetAccessControl("c:\\filename.txt", AccessControlSections.All);
 
// Add a new rule
fs.RemoveAccessRuleAll(new FileSystemAccessRule("Guests", FileSystemRights.Read, AccessControlType.Allow));
//fs.RemoveAccessRule(new FileSystemAccessRule("Guests", FileSystemRights.Read, AccessControlType.Allow));
 
// Save changes
File.SetAccessControl("c:\\filename.txt", fs);

Other Access Rules classes:

EventWaitHandleAccessRule
MutexAccessRule
RegistryAccessRule
SemaphoreAccessRule