"Internal connection fatal error" from TdsParser.TryRun

[initram]

Describe the bug

I am trying to upgrade an older ASP.NET app running on .Net Framework 4.8 to use Microsoft.Data.SqlClient. But when running the app after upgrading I run into errors early during startup. It is able to connect and make requests, but it fails on the forth connection that it makes.

It always fails on the same piece of code (a call to ExecuteScalar()), but if that code is run in isolation, then there are no problems.

Exception message: System.InvalidOperationException: Internal connection fatal error. Error state: 15, Token : 50
Stack trace:   at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.SqlDataReader.TryCloseInternal(Boolean closeReader)
   at Microsoft.Data.SqlClient.SqlDataReader.Close()
   at Microsoft.Data.SqlClient.SqlCommand.CompleteExecuteScalar(SqlDataReader reader, Boolean returnLastResult)
   at Microsoft.Data.SqlClient.SqlCommand.ExecuteScalar()
   at Microsoft.SqlServer.Management.Common.ConnectionManager.ExecuteTSql(ExecuteTSqlAction action, Object execObject, DataSet fillDataSet, Boolean catchException) in /_/src/Microsoft/SqlServer/Management/ConnectionInfo/ConnectionManager.cs:line 808
   at Microsoft.SqlServer.Management.Common.ServerConnection.ExecuteScalar(String sqlCommand) in /_/src/Microsoft/SqlServer/Management/ConnectionInfo/ServerConnection.cs:line 1516
   at Geomatic.Framework.Data.Impl.DbManagement.ExecuteScalar(String sql) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Data\Impl\DbManagement.cs:line 111
   at Geomatic.Framework.Data.Impl.DbManagement.ExecuteScalar[T](String sql) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Data\Impl\DbManagement.cs:line 101
   at Geomatic.Framework.Deployment.DbDeployment.GetVersionFromDatabase(ConnectionDef connectionDef) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 316
   at Geomatic.Framework.Deployment.DbDeployment.IsVersionCompatible(TimestampedDatabase timestampedDatabase, Boolean forRemovingObsoleteDatabases) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 268
   at Geomatic.Framework.Deployment.DbDeployment.<>c__DisplayClass19_0.<GetDatabaseSets>b__0(TimestampedDatabase x) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 223
   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector)
   at Geomatic.Framework.Deployment.DbDeployment.GetDatabaseSets(IList`1 databaseSetNames, Boolean forRemovingObsoleteDatabases) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 221
   at Geomatic.Framework.Deployment.DbDeployment.<GetLatestPrimaryDatabases>d__11.MoveNext() in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 77
   at Geomatic.Framework.Deployment.WebDbDeployment.UpdateCurrentWebAppConnectionStrings()
   at Geomatic.Framework.Deployment.WebDbDeployment.UpdateWebAppConnectionStrings()
   at Geomatic.MosaicProspect.GlobalAsax.Application_Start(Object sender, EventArgs e)]

To reproduce

I do not have a minimal way of reproducing this issue without sending over a lot of code and databases.

I am hoping to find some way of creating a smaller reproducible example, but I am not sure what causes the problem, so it is hard to construct it. Any input would be appreciated.

Expected behavior

I expected it the code to work in a similar fashion to System.Data.SqlClient, or at least get an exception with a helpful message that can be used for debugging. The error that I get leads nowhere and it is very hard for me to know where to look and what to change.

Further technical details

Microsoft.Data.SqlClient version: (found on the nuget or Microsoft.Data.SqlClient.dll)
.NET target: .NET Framework 4.8
SQL Server version: SQL Server 2016
Operating system: Windows 11 client calling the server

Additional context
Connection string is in this format: Data Source=SERVER_NAME;Initial Catalog=DB_NAME;Integrated Security=True;Pooling=False;Encrypt=False (I have also tried without the Pooling=False, it still fails the same way)

Here is the logged output of diagnostics tracing:

2026-05-20 12:44:07,533 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenBefore]: [OperationId, 98d0b7aa-74c7-460e-beb1-c20b690501b4], [Operation, Open], [Timestamp, 1576111278735], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114]
2026-05-20 12:44:07,912 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenAfter]: [OperationId, 98d0b7aa-74c7-460e-beb1-c20b690501b4], [Operation, Open], [Timestamp, 1576115231063], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:07,951 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, 245ce2e6-f9f2-4024-9b55-0c04f07db71d], [Operation, ExecuteReader], [Timestamp, 1576115720932], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,083 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, 245ce2e6-f9f2-4024-9b55-0c04f07db71d], [Operation, ExecuteReader], [Timestamp, 1576116743162], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,121 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseBefore]: [OperationId, 3b8ba6d0-1346-4f89-a156-267448c9940a], [Operation, Close], [Timestamp, 1576117337187], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,131 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseAfter]: [OperationId, 3b8ba6d0-1346-4f89-a156-267448c9940a], [Operation, Close], [Timestamp, 1576117443033], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,139 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenBefore]: [OperationId, 62f03a5b-47ee-454a-8727-9cd8509f6c49], [Operation, Open], [Timestamp, 1576117556101], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114]
2026-05-20 12:44:08,139 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenAfter]: [OperationId, 62f03a5b-47ee-454a-8727-9cd8509f6c49], [Operation, Open], [Timestamp, 1576117593438], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,139 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, f8f941ae-fc97-4b12-b765-c5ce24ecfeea], [Operation, ExecuteReader], [Timestamp, 1576117615849], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,202 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, f8f941ae-fc97-4b12-b765-c5ce24ecfeea], [Operation, ExecuteReader], [Timestamp, 1576118158488], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,202 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseBefore]: [OperationId, 7358b529-bdd8-49ae-852f-46e3115acff0], [Operation, Close], [Timestamp, 1576118224736], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,202 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseAfter]: [OperationId, 7358b529-bdd8-49ae-852f-46e3115acff0], [Operation, Close], [Timestamp, 1576118250841], [ConnectionId, 20931833-8f54-420d-932e-e6a7c3eae471], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,218 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenBefore]: [OperationId, 0d5abfe5-93bb-4de2-9c82-0dab5b438fd4], [Operation, Open], [Timestamp, 1576118411991], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114]
2026-05-20 12:44:08,279 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenAfter]: [OperationId, 0d5abfe5-93bb-4de2-9c82-0dab5b438fd4], [Operation, Open], [Timestamp, 1576118999287], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,316 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, 2ded8a06-8cf0-4f03-a38b-5712091785e9], [Operation, ExecuteReader], [Timestamp, 1576119336915], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,324 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, 2ded8a06-8cf0-4f03-a38b-5712091785e9], [Operation, ExecuteReader], [Timestamp, 1576119385308], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,453 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, e48f4fa4-4dea-43a1-b0db-81409f5907c9], [Operation, ExecuteScalar], [Timestamp, 1576120772614], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,479 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, e48f4fa4-4dea-43a1-b0db-81409f5907c9], [Operation, ExecuteScalar], [Timestamp, 1576120906669], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,644 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, 26654182-8023-4dbd-9183-5c77d9c1a962], [Operation, ExecuteReader], [Timestamp, 1576122582579], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,685 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, 26654182-8023-4dbd-9183-5c77d9c1a962], [Operation, ExecuteReader], [Timestamp, 1576122954784], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,880 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, 6915fba9-3868-45f7-bc54-5ccf8ee1b215], [Operation, ExecuteScalar], [Timestamp, 1576124933736], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,886 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, 6915fba9-3868-45f7-bc54-5ccf8ee1b215], [Operation, ExecuteScalar], [Timestamp, 1576124985343], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,898 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, 189eaa8a-610b-4c91-a4a3-fc16857e0e4e], [Operation, ExecuteReader], [Timestamp, 1576125124667], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,907 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, 189eaa8a-610b-4c91-a4a3-fc16857e0e4e], [Operation, ExecuteReader], [Timestamp, 1576125191594], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,951 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, 8cd248f2-04cd-4cec-9710-88d592a6537c], [Operation, ExecuteReader], [Timestamp, 1576125785922], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:08,966 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, 8cd248f2-04cd-4cec-9710-88d592a6537c], [Operation, ExecuteReader], [Timestamp, 1576125897948], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:08,994 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, 0d5f401f-d008-467c-ae8a-eed4016189b3], [Operation, ExecuteNonQuery], [Timestamp, 1576126086973], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:09,003 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, 0d5f401f-d008-467c-ae8a-eed4016189b3], [Operation, ExecuteNonQuery], [Timestamp, 1576126150329], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:09,004 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, ea1b8540-9be6-40a9-ad3f-73a737597d3f], [Operation, ExecuteReader], [Timestamp, 1576126175309], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:09,012 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandAfter]: [OperationId, ea1b8540-9be6-40a9-ad3f-73a737597d3f], [Operation, ExecuteReader], [Timestamp, 1576126288953], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:09,044 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseBefore]: [OperationId, ff9f7fac-962e-4a55-b29c-21021479b611], [Operation, Close], [Timestamp, 1576126695944], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:09,044 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseAfter]: [OperationId, ff9f7fac-962e-4a55-b29c-21021479b611], [Operation, Close], [Timestamp, 1576126725543], [ConnectionId, e2b83a6e-ea16-4b9e-96b1-1270806baf10], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:09,060 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenBefore]: [OperationId, 84116a96-a81a-4879-8d8f-5fa76140dcd7], [Operation, Open], [Timestamp, 1576126740560], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114]
2026-05-20 12:44:09,091 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionOpenAfter]: [OperationId, 84116a96-a81a-4879-8d8f-5fa76140dcd7], [Operation, Open], [Timestamp, 1576127076320], [ConnectionId, 321c1e95-0c4e-4379-938f-68063da2d0c0], [Connection, Microsoft.Data.SqlClient.SqlConnection], [ClientVersion, 7.0.1.26114], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:09,091 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandBefore]: [OperationId, e52e10f9-2ab7-434f-844e-9cabc8a5e034], [Operation, ExecuteScalar], [Timestamp, 1576127094955], [ConnectionId, 321c1e95-0c4e-4379-938f-68063da2d0c0], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand]
2026-05-20 12:44:09,107 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseBefore]: [OperationId, 70252906-72dd-4e30-83c5-e6311aabb8af], [Operation, Close], [Timestamp, 1576127264744], [ConnectionId, 321c1e95-0c4e-4379-938f-68063da2d0c0], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:09,107 [1] INFO  Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteConnectionCloseAfter]: [OperationId, 70252906-72dd-4e30-83c5-e6311aabb8af], [Operation, Close], [Timestamp, 1576127286640], [ConnectionId, 321c1e95-0c4e-4379-938f-68063da2d0c0], [Connection, Microsoft.Data.SqlClient.SqlConnection], [Statistics, Microsoft.Data.SqlClient.SqlStatistics+StatisticsDictionary]
2026-05-20 12:44:14,012 [1] ERROR Geomatic.Framework.Data.Logging.SqlClientDiagnosticTracing [(null)] - SqlClient [Microsoft.Data.SqlClient.WriteCommandError]: [OperationId, e52e10f9-2ab7-434f-844e-9cabc8a5e034], [Operation, ExecuteScalar], [Timestamp, 1576161247039], [ConnectionId, 321c1e95-0c4e-4379-938f-68063da2d0c0], [TransactionId, ], [Command, Microsoft.Data.SqlClient.SqlCommand], [Exception, System.InvalidOperationException: Internal connection fatal error. Error state: 15, Token : 50
   at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.SqlDataReader.TryCloseInternal(Boolean closeReader)
   at Microsoft.Data.SqlClient.SqlDataReader.Close()
   at Microsoft.Data.SqlClient.SqlCommand.CompleteExecuteScalar(SqlDataReader reader, Boolean returnLastResult)
   at Microsoft.Data.SqlClient.SqlCommand.ExecuteScalar()
   at Microsoft.SqlServer.Management.Common.ConnectionManager.ExecuteTSql(ExecuteTSqlAction action, Object execObject, DataSet fillDataSet, Boolean catchException) in /_/src/Microsoft/SqlServer/Management/ConnectionInfo/ConnectionManager.cs:line 808
   at Microsoft.SqlServer.Management.Common.ServerConnection.ExecuteScalar(String sqlCommand) in /_/src/Microsoft/SqlServer/Management/ConnectionInfo/ServerConnection.cs:line 1516
   at Geomatic.Framework.Data.Impl.DbManagement.ExecuteScalar(String sql) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Data\Impl\DbManagement.cs:line 111
   at Geomatic.Framework.Data.Impl.DbManagement.ExecuteScalar[T](String sql) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Data\Impl\DbManagement.cs:line 101
   at Geomatic.Framework.Deployment.DbDeployment.GetVersionFromDatabase(ConnectionDef connectionDef) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 316
   at Geomatic.Framework.Deployment.DbDeployment.IsVersionCompatible(TimestampedDatabase timestampedDatabase, Boolean forRemovingObsoleteDatabases) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 268
   at Geomatic.Framework.Deployment.DbDeployment.<>c__DisplayClass19_0.<GetDatabaseSets>b__0(TimestampedDatabase x) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 223
   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector, IEqualityComparer`1 comparer)
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable`1 source, Func`2 keySelector, Func`2 elementSelector)
   at Geomatic.Framework.Deployment.DbDeployment.GetDatabaseSets(IList`1 databaseSetNames, Boolean forRemovingObsoleteDatabases) in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 221
   at Geomatic.Framework.Deployment.DbDeployment.<GetLatestPrimaryDatabases>d__11.MoveNext() in C:\dev\Development\src\Framework\app\Geomatic.Framework\Deployment\DbDeployment.cs:line 77
   at Geomatic.Framework.Deployment.WebDbDeployment.UpdateCurrentWebAppConnectionStrings()
   at Geomatic.Framework.Deployment.WebDbDeployment.UpdateWebAppConnectionStrings()
   at Geomatic.MosaicProspect.GlobalAsax.Application_Start(Object sender, EventArgs e)]

[github-actions]

🔍 Triage Summary

Check	Result
Issue type	Bug
Environment	⚠️ Missing: Exact Microsoft.Data.SqlClient NuGet version (template field left as placeholder — version 7.0.1.26114 is visible in the diagnostics trace log)
Area	Area\Netfx
Duplicates	None found (issue #919 has a similar error message but refers to System.Data.SqlClient with a different token and a different root cause)
Regression	Likely regression from System.Data.SqlClient — worked previously, fails after migration to Microsoft.Data.SqlClient

Analysis

The reporter is migrating an ASP.NET app from System.Data.SqlClient to Microsoft.Data.SqlClient 7.0.1 on .NET Framework 4.8. The error System.InvalidOperationException: Internal connection fatal error. Error state: 15, Token : 50 is thrown inside TdsParser.TryRun during SqlDataReader.Close() / CompleteExecuteScalar, but only when multiple connections are made in sequence during application startup (specifically the 4th connection). Pooling is disabled, the connection uses Integrated Security against SQL Server 2016, and the issue does not reproduce in isolation. This points to a TDS state machine issue specific to the .NET Framework code path, possibly related to how TdsParser handles token 50 (an unknown/unexpected TDS token during reader cleanup). Severity: P2 — application startup is blocked after migration.

Next Steps

• @initram, please confirm the exact NuGet version used (e.g. 7.0.1 or 7.0.0) so we can check changelogs for any related fixes.
• Assign this issue to the Copilot coding agent to investigate TdsParser.TryRun on the .NET Framework code path — specifically how TDS token 0x32 (decimal 50) is handled during SqlDataReader.TryCloseInternal. The fact that it only occurs on the 4th connection in a sequence (even with Pooling=False) may suggest shared parser/session state or a login-token negotiation side-effect in the .netfx path that differs from System.Data.SqlClient. The agent should also check whether SQL Server 2016 sends any login-response tokens that the newer driver doesn't expect or handle correctly.
• If possible, try capturing a network trace (e.g. with Wireshark or netsh trace) or enable SqlClientDiagnosticTracing at TRACE level to capture what token is received just before the error.

Note: This triage summary is auto-generated by an AI agent. The analysis and suggestions above have not been verified by a human maintainer. Please treat as preliminary guidance only.

Generated by SqlClient Issue Auto-Triage for issue #4299 · ● 3.7M · ◷

[initram]

I am using Microsoft.Data.SqlClient version 7.0.1 from nuget.

[dallmair]

Same here, both 7.0.0 and 7.0.1 on .NET 4.8 fail this way, haven't tried older versions. Tried to connect to both SQL Server 2019 as well as SQL Server 2025.