Add group to an computer object security tab AD

[whippet]

Hi,
When you create a computer account in Active Directory (manually), you can change "The following user or group can join this computer to a domain". When you do this, the user or group is added to the security tab.

I would like to do this with c# (automatically) and I cannot find a solution.

Thank you for your help
Sorry! I'm not an english people.

[whippet]

Hi,
I receive this error message : Object reference not set an instance of an object.

My code :

DirectoryEntry computers = new DirectoryEntry(sLDAP + PCTarget, "Domain" + "\\" + "user", "Password", AuthenticationTypes.Secure);
computers.Options.SecurityMasks = SecurityMasks.Owner | SecurityMasks.Group | SecurityMasks.Dacl | SecurityMasks.Sacl;

try
{
ActiveDirectorySecurity sdc = computers.ObjectSecurity;
NTAccount Account = new NTAccount("Domain\\MyGroupName");
SecurityIdentifier Sid = (SecurityIdentifier)Account.Translate(typeof(Secur ityIdentifier));
ActiveDirectoryAccessRule rule = new ActiveDirectoryAccessRule(Sid,ActiveDirectoryRight s.ExtendedRight | ActiveDirectoryRights.GenericRead,AccessControlTyp e.Allow);
The message appears when the SetAccesRule is executed!!!
sdc.SetAccessRule(rule);
computers.CommitChanges();
computers.Close();
computers.Dispose();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message.ToString());
}

Thank you