Microsoft.Data.SqlClient.SqlConnection.OpenAsync throws error saying "The given key was not present in the dictionary."

Question

This error started suddenly after upgrading Microsoft.Data.SqlClient from v2 to v4. Reverting the code back had no effect and the error persists. It's a basic connection string with a data source, initial catalog, username, password, and MARS. Identical settings work fine when connecting through SSMS, so it's not a permissions issue; this has all be working fine for a long time.

Encryption is off by default. The only strange thing I noticed coinciding with this error (other than the client version update, which I suspect corrupted something) is that if I turn on encryption, I get an error about a certificate chain being invalid. The only root certificate I can find that expired recently was a GlobalSign root cert. I've since updated Windows and the error persists.

StackTrace:

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()

Answer 1

It's not posted as an answer, so even if not from my head, let's keep track of what is working.

If you're using Microsoft.Data.SqlClient library with .NET Framework v4 against a SQL cluster (eg. utilizing Availability Groups) you have to add blank Failover Partner=; parameter. Can be added via ConnectionBuilder too.

Answer 2

This is reportedly fixed in Microsoft.Data.SqlClient 5.0.0 (released Aug 5th 2022).

https://github.com/dotnet/SqlClient/blob/main/release-notes/5.0/5.0.0.md https://github.com/dotnet/SqlClient/pull/1614