EWS Oauth 异常：请求失败。远程服务器返回错误：(401) Unauthorized

Question

我正在尝试创建一个可以预订会议的机器人。为此，我需要访问员工的日历以获取 FreeBusy 信息以最终预订会议。我试图避免对电子邮件和密码进行硬编码，为此我想使用 Azure AD 中的访问令牌来调用 EWS。 我为

设置属性

public static ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2013);

使用这种方法：

       public static async System.Threading.Tasks.Task UseExchangeService(IDialogContext context, string userEmailAddress, SecureString     userPassword)
         {
        string authority = ConfigurationManager.AppSettings["authority"];
        string clientID = ConfigurationManager.AppSettings["clientID"];
         string resource = ConfigurationManager.AppSettings["resource"];
        string appKey = ConfigurationManager.AppSettings["appkey"];

        AuthenticationContext authenticationContext = new AuthenticationContext(authority, false);
        ClientCredential clientCred = new ClientCredential(clientID, appKey);
        AuthenticationResult authenticationResult = await authenticationContext.AcquireTokenAsync(resource, clientCred);
        service.Url = new Uri(ConfigurationManager.AppSettings["serverName"] + "/ews/exchange.asmx");
        service.TraceEnabled = true;
        service.TraceFlags = TraceFlags.All;
        service.Credentials = new OAuthCredentials(authenticationResult.AccessToken);


        // USING THIS LINE IT WORKS FINE!
        // service.Credentials = new NetworkCredential(userEmailAddress, userPassword); // VIRKER

    }

我确实从 Azure AD 获得了访问令牌，并且我已授予 Azure AD 中应用程序的权限。

我使用这种方法来提取空闲时间，它包含其他更多代码来将时间显示为 herocard 上的按钮，但这是对 EWS 的调用：

       List<AttendeeInfo> attendees = new List<AttendeeInfo>();
        attendees.Add(new AttendeeInfo()
        {
            SmtpAddress = "MyEMAIL",
            AttendeeType = MeetingAttendeeType.Organizer
        });

        attendees.Add(new AttendeeInfo()
        {
            SmtpAddress = BookersEmail,
            AttendeeType = MeetingAttendeeType.Required
        });
        //DateTime date1 = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day.Ad, 7, 0, 0)
        // Specify options to request free/busy information and suggested meeting times.
        AvailabilityOptions availabilityOptions = new AvailabilityOptions();
        availabilityOptions.GoodSuggestionThreshold = 49;
        availabilityOptions.MaximumNonWorkHoursSuggestionsPerDay = 0;
        availabilityOptions.MaximumSuggestionsPerDay = 20;
        // Note that 60 minutes is the default value for MeetingDuration, but setting it explicitly for demonstration purposes.
        availabilityOptions.MeetingDuration = 60;
        availabilityOptions.MinimumSuggestionQuality = SuggestionQuality.Excellent;

        //TimeWindow hej = new TimeWindow();
        DateTime StartDay = DateTime.Now.AddDays(1);
        TimeSpan ts = new TimeSpan(9, 0, 0);
        DateTime StartTime = StartDay.Date + ts;

        availabilityOptions.DetailedSuggestionsWindow = new TimeWindow(StartTime, DateTime.Now.AddDays(4));
        availabilityOptions.RequestedFreeBusyView = FreeBusyViewType.FreeBusy;
        // Return free/busy information and a set of suggested meeting times. 
        // This method results in a GetUserAvailabilityRequest call to EWS.
        GetUserAvailabilityResults results = service.GetUserAvailability(attendees,
                                                                         availabilityOptions.DetailedSuggestionsWindow,
                                                                         AvailabilityData.FreeBusyAndSuggestions,
                                                                         availabilityOptions);

我在 Azure AD 中创建了应用程序，并授予了以下权限： Office 365 在线交换：

使用对所有邮箱具有完全访问权限的 Exchange Web 服务

在所有邮箱中读写日历

读写用户和共享日历

通过 Exchange Web 服务以登录用户身份访问邮箱

我已经尝试过在 stackoverflow 上找到的其他答案，但是它们对我没有用。 希望你能帮忙

Answer 1

我不熟悉 EWS，但据我所知，Microsoft Graph 也提供了类似的功能，可以使用下面的其余部分查找可用的会议时间（请参阅 here）：

POST /me/findMeetingTimes

如果您想将此 REST 用于 Web 应用程序，以便您的 Web 应用程序可以委托登录用户执行 Exchange 操作，我们可以使用 OAuth 2.0 代码授权流程 .而关于如何使用此流程与 Microsoft Graph 集成，您可以参考以下链接：

Get started with Microsoft Graph in an ASP.NET 4.6 MVC app

以下是此流程的详细信息：

Authorize access to web applications using OAuth 2.0 and Azure Active Directory

希望对你有帮助。