C#:ActiveDirectory : Check User cannot change password

in project add COM reference to "Active DS Type Library" COM library v1.0
usually located in C:\WINDOWS\system32\activeds.tlb.

using ActiveDs;
        public void CheckUserCanChangePasswordsProperty()
        {
            DirectoryEntry de = GetDirectoryObject(UserName);
            string PASSWORD_GUID = "{ab721a53-1e2f-11d0-9819-00aa0040529b}";
            string[] trustees = { "NT AUTHORITY\\SELF", "EVERYONE" };


            ActiveDs.IADsSecurityDescriptor sd =
                (ActiveDs.IADsSecurityDescriptor)de.Properties["ntSecurityDescriptor"].Value;
            ActiveDs.IADsAccessControlList acl = (ActiveDs.IADsAccessControlList)sd.DiscretionaryAcl;
            ActiveDs.AccessControlEntry ace = new ActiveDs.AccessControlEntry();


            double denied = (double)ActiveDs.ADS_ACETYPE_ENUM.ADS_ACETYPE_ACCESS_DENIED_OBJECT;
            double objectType = (double)ActiveDs.ADS_FLAGTYPE_ENUM.ADS_FLAG_OBJECT_TYPE_PRESENT;
            double dsControl = (double)ActiveDs.ADS_RIGHTS_ENUM.ADS_RIGHT_DS_CONTROL_ACCESS;

            foreach (string trustee in trustees)
            {
                ace.Trustee = trustee;
                ace.AceFlags = 0;
                ace.AceType = Convert.ToInt32(Math.Floor(denied));
                ace.Flags = Convert.ToInt32(Math.Floor(objectType));
                ace.ObjectType = PASSWORD_GUID;
                ace.AccessMask = Convert.ToInt32(Math.Floor(dsControl));

                acl.AddAce(ace);
            }
            sd.DiscretionaryAcl = acl;
            de.Properties["ntSecurityDescriptor"].Value = sd;

            de.CommitChanges();
        }

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C#:Active Directory:Uncheck User cannot change password

        public void SetUserCanChangePasswordsPropertyUncheck()
        {
            DirectoryEntry de = GetDirectoryObject(UserName);
            string PASSWORD_GUID = "{ab721a53-1e2f-11d0-9819-00aa0040529b}";
            ActiveDs.IADsSecurityDescriptor sd =
                (ActiveDs.IADsSecurityDescriptor)de.Properties["ntSecurityDescriptor"].Value;
            ActiveDs.IADsAccessControlList acl = (ActiveDs.IADsAccessControlList)sd.DiscretionaryAcl;
            //ActiveDs.AccessControlEntry ace = new ActiveDs.AccessControlEntry();
            ActiveDs.ADS_ACETYPE_ENUM aceType;

            //look for existing ace and get rid of
            foreach (ActiveDs.AccessControlEntry ace in acl)
            {
                if (!(ace.ObjectType == null) && ace.ObjectType.ToLower() == PASSWORD_GUID)
                {
                    if (ace.Trustee == "Everyone")
                    {
                        acl.RemoveAce(ace);
                        de.CommitChanges();
                    }
                    else if (ace.Trustee == "NT AUTHORITY\\SELF")
                    {
                        acl.RemoveAce(ace);
                        de.CommitChanges();
                    }
                }
            }

            //now put in the one we want                
            sd.DiscretionaryAcl = acl;
            de.Properties["ntSecurityDescriptor"].Value = sd;
            de.CommitChanges();
        }

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C#:Active Directory:Check/Uncheck Password never expires

        public void SetPasswordNeverExpiresProperty(bool PasswordNeverExpires)
        {
            DirectoryEntry de = GetDirectoryObject(UserName);
            if (PasswordNeverExpires)
            {
                ActiveDirectoryHelper.SetProperty(de, "userAccountControl",
                                                  (int)de.Properties["userAccountControl"].Value | 0x10000);
            }
            else
            {
                ActiveDirectoryHelper.SetProperty(de, "userAccountControl",
                                                  (int)de.Properties["userAccountControl"].Value ^ 0x10000);
            }
            de.CommitChanges();
        }

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C#:Active Directory:Check/Uncheck User must change password at next logon

        public void SetuserHasToChangePasswordsInTheNextLoginProperty(bool userHasToChangePasswordsInTheNextLogin)
        {
            DirectoryEntry de = GetDirectoryObject(UserName);
            if (userHasToChangePasswordsInTheNextLogin)
            {
                ActiveDirectoryHelper.SetProperty(de, "pwdLastSet", 0);
            }
            else
            {
                ActiveDirectoryHelper.SetProperty(de, "pwdLastSet", -1);
            }
            de.CommitChanges();
        }

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authentication in active directory

using System.Security;
        public User Login(string login_name, string password){
            ICredValidator cv = new LdapCredValidator(); //LanCredValidator();
            User u = new User(conn);
            if (cv.ValidateCred("MY-DOM", login_name, password))
            {
                // validation sucess
            }else Throw("Login failed for {0}",login_name);
            return u;
        }

active directory - get computer lists

 public void AD_ComputerList()
        {
            DirectoryEntry entry = new DirectoryEntry("LDAP://my-dom");
            DirectorySearcher mySearcher = new DirectorySearcher(entry);
            mySearcher.Filter = ("(objectClass=computer)");
            Console.WriteLine("Listing of computers in the Active Directory");
            Console.WriteLine("============================================");
            foreach(SearchResult resEnt in mySearcher.FindAll())
            {
                Console.WriteLine("Name: {0}", resEnt.GetDirectoryEntry().Name.ToString());
            }
            Console.WriteLine("=========== End of Listing =============");

        }

C# how to get current windows login

  public void WinIdentity() {
           System.Security.Principal.WindowsIdentity i = System.Security.Principal.WindowsIdentity.GetCurrent();
            Console.WriteLine("name: {0}, token: {1}", i.Name, i.Groups[0].ToString());
            Assert.IsNotNull(i);
        }