SqlClient: System.AccessViolationException at SNIOpenSyncExWrapper

Description

When connecting to a SQL instance in Azure App Services if the connection fails we don’t get a graceful connection error but we recieve the following exception.

This code is .NET Framework 4.8 Deployed to Azure App Services

Application: w3wp.exe
Framework Version: v4.0.30319
Description: System.AccessViolationException
Exception message: The process was terminated due to an unhandled exception.
Stack trace:

Exception Info: System.AccessViolationException
   at <Module>.SNIOpenSyncExWrapper(SNI_CLIENT_CONSUMER_INFO*, SNI_ConnWrapper**)
   at SNINativeMethodWrapper.SNIOpenSyncEx(ConsumerInfo, System.String, IntPtr ByRef, Byte[], Byte[], Boolean, Boolean, Int32, Boolean, Int32, Int32, Boolean)
   at System.Data.SqlClient.SNIHandle..ctor(ConsumerInfo, System.String, Byte[], Boolean, Int32, Byte[] ByRef, Boolean, Boolean, Boolean, System.Data.SqlClient.TransparentNetworkResolutionState, Int32)
   at System.Data.SqlClient.TdsParserStateObject.CreatePhysicalSNIHandle(System.String, Boolean, Int64, Byte[] ByRef, Byte[], Boolean, Boolean, Boolean, System.Data.SqlClient.TransparentNetworkResolutionState, Int32)
   at System.Data.SqlClient.TdsParser.Connect(System.Data.SqlClient.ServerInfo, System.Data.SqlClient.SqlInternalConnectionTds, Boolean, Int64, Boolean, Boolean, Boolean, Boolean, Boolean, System.Data.SqlClient.SqlAuthenticationMethod, Boolean, System.Data.SqlClient.SqlAuthenticationProviderManager)
   at System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(System.Data.SqlClient.ServerInfo, System.String, System.Security.SecureString, Boolean, System.Data.ProviderBase.TimeoutTimer, Boolean, Boolean, Boolean)
   at System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(System.Data.SqlClient.ServerInfo, System.String, System.Security.SecureString, Boolean, System.Data.SqlClient.SqlConnectionString, System.Data.SqlClient.SqlCredential, System.Data.ProviderBase.TimeoutTimer)
   at System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(System.Data.ProviderBase.TimeoutTimer, System.Data.SqlClient.SqlConnectionString, System.Data.SqlClient.SqlCredential, System.String, System.Security.SecureString, Boolean)
   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(System.Data.ProviderBase.DbConnectionPoolIdentity, System.Data.SqlClient.SqlConnectionString, System.Data.SqlClient.SqlCredential, System.Object, System.String, System.Security.SecureString, Boolean, System.Data.SqlClient.SqlConnectionString, System.Data.SqlClient.SessionData, System.Data.ProviderBase.DbConnectionPool, System.String, Boolean, System.Data.SqlClient.SqlAuthenticationProviderManager)
   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(System.Data.Common.DbConnectionOptions, System.Data.Common.DbConnectionPoolKey, System.Object, System.Data.ProviderBase.DbConnectionPool, System.Data.Common.DbConnection, System.Data.Common.DbConnectionOptions)
   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(System.Data.ProviderBase.DbConnectionPool, System.Data.Common.DbConnection, System.Data.Common.DbConnectionOptions, System.Data.Common.DbConnectionPoolKey, System.Data.Common.DbConnectionOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(System.Data.Common.DbConnection, System.Data.Common.DbConnectionOptions, System.Data.ProviderBase.DbConnectionInternal)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(System.Data.Common.DbConnection, System.Data.Common.DbConnectionOptions, System.Data.ProviderBase.DbConnectionInternal)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(System.Data.Common.DbConnection, UInt32, Boolean, Boolean, System.Data.Common.DbConnectionOptions, System.Data.ProviderBase.DbConnectionInternal ByRef)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(System.Data.Common.DbConnection, System.Threading.Tasks.TaskCompletionSource`1<System.Data.ProviderBase.DbConnectionInternal>, System.Data.Common.DbConnectionOptions, System.Data.ProviderBase.DbConnectionInternal ByRef)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(System.Data.Common.DbConnection, System.Threading.Tasks.TaskCompletionSource`1<System.Data.ProviderBase.DbConnectionInternal>, System.Data.Common.DbConnectionOptions, System.Data.ProviderBase.DbConnectionInternal, System.Data.ProviderBase.DbConnectionInternal ByRef)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(System.Data.Common.DbConnection, System.Data.ProviderBase.DbConnectionFactory, System.Threading.Tasks.TaskCompletionSource`1<System.Data.ProviderBase.DbConnectionInternal>, System.Data.Common.DbConnectionOptions)
   at System.Data.SqlClient.SqlConnection.TryOpenInner(System.Threading.Tasks.TaskCompletionSource`1<System.Data.ProviderBase.DbConnectionInternal>)
   at System.Data.SqlClient.SqlConnection.TryOpen(System.Threading.Tasks.TaskCompletionSource`1<System.Data.ProviderBase.DbConnectionInternal>)
   at System.Data.SqlClient.SqlConnection.Open()
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.TimerQueueTimer.CallCallback()
   at System.Threading.TimerQueueTimer.Fire()
   at System.Threading.TimerQueue.FireNextTimers()

To reproduce

Include a complete code listing (or project/solution) that we can run to reproduce the issue.

Partial code listings, or multiple fragments of code, will slow down our response or cause us to push the issue back to you to provide code to reproduce the issue.

private static bool TestConnection(string connectionString)
{
    const string SqlQuery = "SELECT TOP 1 message_id FROM sys.messages";
	
    try
    {
        using (var connection = new SqlConnection(connectionString))
        {
            connection.Open();

            using (var sqlCommand = new SqlCommand(SqlQuery, connection) {CommandType = CommandType.Text})
            {
                return sqlCommand.ExecuteReader().HasRows;
            }
        }
    }
    catch (Exception ex)
    {
        _logger.LogError(ex);
        throw;
    }
}

Expected behavior

I’d expect if we’re having issues connecting to a SQL instance that a sensible error is returned. As the System.AccessViolationException bypasses the try { } catch { } due to behaviour changes in .NET Framework 4 we don’t want to set legacyCorruptedStateExceptionsPolicy due to the impact it would have on other exceptions.

Correct handling of the connection error and appropriate SQL exception raised back to the caller.

Further technical details

Microsoft.Data.SqlClient version: (found on the nuget or Microsoft.Data.SqlClient.dll) .NET target: Framework 4.8 SQL Server version: SQL Server 2017 (Distributed Availability Group) Operating system: App Services Windows