本文转自： https://www.cnblogs.com/i-mengli/p/9625551.html 

        //获取登陆页输入的域账号、密码
        string domainIP = "192.168.12.10";　　　　　　//域IP
        string userAccount = "Administrator";　　　　//域账号
        string Password = "glyszsuzhou";　　　　　　//域账号密码 　　　　　　　　　
        using (DirectoryEntry deUser = new DirectoryEntry(@"LDAP://" + domainIP, userAccount, Password))
        {
            DirectorySearcher src = new DirectorySearcher(deUser);
            src.Filter = "(&(&(objectCategory=person)(objectClass=user))(sAMAccountName=" + userAccount + "))";
            src.PropertiesToLoad.Add("cn");
            src.SearchRoot = deUser;
            src.SearchScope = SearchScope.Subtree;

            SearchResult result = src.FindOne();
            if (result != null)//验证成功
            {
                DirectoryEntry de = result.GetDirectoryEntry();
                string userID = de.Username;
                #region 域账号验证通过后判断是否用户在本系统中
                var existUser = new DAL.Maintain.UserOP().GetData(userID);
                if (existUser == null)
                {
                    ViewBag.ErrorInfo = "提示：您未开通系统的权限，请联系管理员。<br/>You have no access to the system, please contact the administrator!";
                    return View();
                }
                #endregion

                FormsAuthentication.SetAuthCookie(userID, false);
                Session.Add("UserID", userID);
                Logger.DefaultLog.Info("登陆sessionUserID:" + Session["UserID"].ToString());

                if (string.IsNullOrEmpty(ReturnUrl))
                {
                    return Redirect(Url.Action("Index", "Home"));
                }
                else
                {
                    //...
                }
            }
            else
            {
                ViewBag.ErrorInfo = "提示：登录失败: 未知的用户名或错误密码。<br/>Account or Password is incorrect!";
                return View();
            }

        }