我一直在开发一个程序,该程序可以扫描交换收件箱以查找来自指定地址的特定电子邮件。目前,该程序读取收件箱、下载附件并将电子邮件移动到另一个文件夹。但是,在从 EWS 服务器拉取大约 15 次后,连接开始出现 401 未经授权的错误,直到我重新启动程序。该程序设置为通过 OAuth 登录,因为系统管理员禁用了基本身份验证。下面是我用来获取交换连接并从收件箱中读取电子邮件的代码。
交换连接代码:
public static async Task<ExchangeService> GetExchangeConnection()
{
var pcaOptions = new PublicClientApplicationOptions
{
ClientId = AppID,
TenantId = TenantID,
};
var pca = PublicClientApplicationBuilder.CreateWithApplicationOptions(pcaOptions).Build();
var ewsScopes = new string[] { "https://outlook.office365.com/EWS.AccessAsUser.All" };
var securePassword = new SecureString();
foreach (char c in Pasword)
securePassword.AppendChar(c);
try
{
var authResult = await pca.AcquireTokenByUsernamePassword(ewsScopes, Username, securePassword).ExecuteAsync();
ExchangeService exchangeService = new ExchangeService()
{
Credentials = new OAuthCredentials(authResult.AccessToken),
Url = new Uri("https://outlook.office365.com/ews/exchange.asmx"),
};
return exchangeService;
}
catch
{
return null;
}
}
电子邮件检索器
public static List<Email> RetreiveEmails()
{
ExchangeService exchangeConnection = GetExchangeConnection().Result;
try
{
List<Email> Emails = new List<Email>();
TimeSpan ts = new TimeSpan(0, -5, 0, 0);
DateTime date = DateTime.Now.Add(ts);
SearchFilter.IsGreaterThanOrEqualTo EmailTimeFilter = new SearchFilter.IsGreaterThanOrEqualTo(ItemSchema.DateTimeReceived, date);
if (exchangeConnection != null)
{
FindItemsResults<Item> findResults = exchangeConnection.FindItems(WellKnownFolderName.Inbox, EmailTimeFilter, new ItemView(10));
foreach (Item item in findResults)
{
if (item.Subject != null)
{
EmailMessage message = EmailMessage.Bind(exchangeConnection, item.Id);
message.Load(new PropertySet(BasePropertySet.FirstClassProperties, ItemSchema.TextBody));
Emails.Add(new Email(message.DateTimeReceived, message.From.Name.ToString(), message.Subject, message.TextBody.ToString(), (message.HasAttachments) ? "Yes" : "No", message.Id.ToString()));
}
}
}
exchangeConnection = null;
return Emails;
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
return null;
}
}
当电子邮件检索器尝试创建交换连接或从文件夹请求电子邮件时,会发生错误。在任何一种情况下,代码都会出错,并在使用前十几次有效的凭据时给我 401 未经授权,然后在多次尝试后失败。我已经尝试使用多个不同的帐户,但问题仍然存在,并且我已确保该应用程序有权访问交换收件箱。非常感谢任何建议或帮助。
答案 0 :(得分:0)
在对 401 错误进行进一步跟踪后,导致令牌出现问题,其 1 小时寿命已结束。这是因为原始 OAuth 令牌的初始生命周期为 1 小时。然而,这可以通过设置代码在需要时自动刷新令牌来解决。这是为遇到此问题的任何其他人解决此问题的代码。
身份验证管理器:
class AuthenticationManager
{
protected IPublicClientApplication App { get; set; }
public AuthenticationManager(IPublicClientApplication app)
{
App = app;
}
public async Task<AuthenticationResult> AcquireATokenFromCacheOrUsernamePasswordAsync(IEnumerable<String> scopes, string username, SecureString password)
{
AuthenticationResult result = null;
var accounts = await App.GetAccountsAsync();
if (accounts.Any())
{
try
{
result = await (App as PublicClientApplication).AcquireTokenSilent(scopes, accounts.FirstOrDefault()).ExecuteAsync();
}
catch (MsalUiRequiredException)
{ }
}
if (result == null)
{
result = await (App as PublicClientApplication).AcquireTokenByUsernamePassword(scopes, username, password).ExecuteAsync();
}
return result;
}
}
我使用的是直接用户名和密码身份验证,但代码行也可以切换为通过交互式方法获取用户身份验证。该代码本质上创建了身份验证管理器的一个新实例,其中包含用于初始化它的 PublicClientApplication,其中包含 appID 和租户 ID。初始化后,您可以调用 AquireATokenFromCacheOrUsernamePasswordAsync,它会尝试查看是否存在一个帐户来获取令牌。接下来,它会尝试检索先前缓存的令牌,或者如果令牌在 5 分钟内到期,则刷新该令牌。如果有可用的令牌,它将返回给主应用程序。如果没有可用的令牌,它将使用提供的用户名和密码获取新令牌。这段代码的实现看起来像这样,
class ExchangeServices
{
AuthenticationManager Manager = null;
public ExchangeServices(String AppId, String TenantID)
{
var pcaOptions = new PublicClientApplicationOptions
{
ClientId = AppID,
TenantId = TenantID,
};
var pca = PublicClientApplicationBuilder.CreateWithApplicationOptions(pcaOptions).Build();
Manager = new AuthenticationManager(pca);
}
public static async Task<ExchangeService> GetExchangeService()
{
var ewsScopes = new string[] { "https://outlook.office365.com/EWS.AccessAsUser.All" }
var securePassword = new SecureString();
foreach(char c in Password)
securePassword.AppendChar(c);
var authResult = await Manager.AquireATokenFromCacheOrUsernamePasswordAsync(ewsScopes, Username, securePassword);
ExchangeService exchangeService = new ExchangeService()
{
Credentials = new OAuthCredentials(authResult.AccessToken),
Url = new Uri("https://outlook.office365.com/ews/exchange.asmx");
};
return exchangeService;
}
}
上面的代码是创建新的身份验证管理器并在通过 OAuth 使用 EWS 服务时使用它来获取和更新新令牌所需的一切。这是我找到的解决上述问题的解决方案。