C# ADSI高手帮帮我

Question

DirectoryEntry de = new DirectoryEntry(ldap, "Administrator", "Password");
                DirectoryEntry newuser = new DirectoryEntry();
                DirectoryEntries users = de.Children;
                DirectoryEntry user = users.Add("CN=" + txtUserMail.Text.Trim(), "user");                user.Properties["userPrincipalName"].Add(txtUserMail.Text.Trim());
                user.Properties["name"].Add(txtUserName.Text.Trim());
                user.Properties["sn"].Add(txtUserSn.Text.Trim());
                user.Properties["givenname"].Add(txtUserGiven.Text.Trim());
                user.Properties["displayname"].Add(txtUserSn.Text.Trim()+ txtUserGiven.Text.Trim());                user.CommitChanges();  我在自己机器上装了个虚拟机，权限肯定够。但是就是添加完user后，该user在ActiveDirectory里打了个红叉，“该帐户被禁用”。手动启用就没问题了。
请问在程序里怎么做才能在添加后就自动启用呢？