c# - 从ExchangeWebService基本身份验证迁移到OAuth2.0

与微软通电话后，他们努力地帮助我使其正常运行。花了一段时间，但是我终于能够使用以下代码建立与Microsoft Services的OAuth连接：

private const string TenantID = "[Your Tenant ID]";
private const string ClientID = "[Your Client ID]";
private const string ClientSecret = "[Your Secret ID]";

private const string AgentName = "My Agent Name";

public static ExchangeService OAuthConnectPost()
{
    string LoginURL = String.Format("https://login.microsoftonline.com/{0}/oauth2/v2.0/token", TenantID);

    var LogValues = new Dictionary<string, string>
    {
        { "grant_type", "client_credentials" },
        { "client_id", ClientID },
        { "client_secret", ClientSecret },
        { "scope", "https://graph.microsoft.com/.default" }
    };
    string postData = "";
    foreach (var v in LogValues)
    {
        postData += (String.IsNullOrWhiteSpace(postData) ? "" : "&") + v.Key + "=" + v.Value;
    }
    var data = Encoding.ASCII.GetBytes(postData);

    ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
    ServicePointManager.Expect100Continue = true;
    ServicePointManager.DefaultConnectionLimit = 9999;
    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls
       | SecurityProtocolType.Tls11
       | SecurityProtocolType.Tls12
       | SecurityProtocolType.Ssl3;

    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(LoginURL);
    request.Method = "POST";
    request.ContentType = "application/x-www-form-urlencoded";
    request.Accept = "*/*";
    request.UserAgent = AgentName;
    request.CachePolicy = new RequestCachePolicy(RequestCacheLevel.NoCacheNoStore);
    request.ContentLength = data.Length;
    using (var stream = request.GetRequestStream())
    {
        stream.Write(data, 0, data.Length);
    }

    using (var response = (HttpWebResponse)request.GetResponse())
    using (Stream stream = response.GetResponseStream())
    using (var reader = new StreamReader(stream))
    {
        var json = reader.ReadToEnd();
        var aToken = JObject.Parse(json)["access_token"].ToString();

        var ewsClient = new ExchangeService();
        ewsClient.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");
        ewsClient.Credentials = new OAuthCredentials(aToken);
        return ewsClient;
    }
}

然后，我可以连接到该服务并使用类似于我之前所做的用户帐户进行身份验证

var service = OAuthConnectPost();
service.Credentials = new WebCredentials(EmailBox, EmailPass, EmailDomain);
FolderId rootFolderId = new FolderId(WellKnownFolderName.Inbox);
ItemView view = new ItemView(500);
FindItemsResults<Item> findResults = service.FindItems(rootFolderId, view);