将 Microsoft.Data.SqlClient 从 v2 升级到 v4 后突然出现此错误。恢复代码没有效果，错误仍然存在。它是一个包含数据源、初始目录、用户名、密码和 MARS 的基本连接字符串。通过 SSMS 连接时，相同的设置可以正常工作，因此这不是权限问题；长期以来，这一切都很好。
加密默认关闭。我注意到与此错误同时发生的唯一奇怪的事情（除了客户端版本更新，我怀疑它损坏了某些东西）是，如果我打开加密，我会收到一个关于证书链无效的错误。我能找到的唯一一个最近过期的根证书是 GlobalSign 根证书。我已经更新了 Windows 并且错误仍然存在。
堆栈跟踪：
at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
at Microsoft.Data.SqlClient.SqlConnectionPoolGroupProviderInfo.CreateFailoverPermission(SqlConnectionString userConnectionOptions, String actualFailoverPartner)
at Microsoft.Data.SqlClient.SqlConnectionPoolGroupProviderInfo.FailoverCheck(Boolean actualUseFailoverPartner, SqlConnectionString userConnectionOptions, String actualFailoverPartner)
at Microsoft.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout)
at Microsoft.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
at Microsoft.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, ServerCertificateValidationCallback serverCallback, ClientCertificateRetrievalCallback clientCallback, DbConnectionPool pool, String accessToken, SqlClientOriginalNetworkAddressInfo originalNetworkAddressInfo, Boolean applyTransientFaultHandling)
at Microsoft.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
at Microsoft.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
at Microsoft.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
at Microsoft.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at Microsoft.Data.ProviderBase.DbConnectionPool.WaitForPendingOpen()
--- End of stack trace from previous location ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable.ConfiguredTaskAwaiter.GetResult()
at ConnectionRunner.ConnectionInfo.<OpenAsync>d__39.MoveNext()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()
at ConnectionRunner.ConnectionInfo.<TestConnectionAsync>d__35.MoveNext()