Fix | Addressing the excepted behavior when error class is greater than 20 on retry connecting

src/Microsoft.Data.SqlClient/netcore/src/Microsoft/Data/SqlClient/SqlConnection.cs

@@ -1414,6 +1414,12 @@ private async Task ReconnectAsync(int timeout)
                         if (attempt == retryCount - 1)
                         {
                             SqlClientEventSource.Log.TryTraceEvent("SqlConnection.ReconnectAsync | Info | Original Client Connection Id {0}, give up reconnection", _originalConnectionId);
+                            if (e.Class >= TdsEnums.FATAL_ERROR_CLASS)
+                            {
+                                SqlClientEventSource.Log.TryTraceEvent("<sc.SqlConnection.ReconnectAsync|INFO> Original ClientConnectionID {0} - Fatal Error occured. Error Class: {1}", _originalConnectionId, e.Class);
+                                // Error Class: 20-25, usually terminates the database connection
+                                InnerConnection.CloseConnection(InnerConnection.Owner, ConnectionFactory);
+                            }
                             throw SQL.CR_AllAttemptsFailed(e, _originalConnectionId);
                         }
                         if (timeout > 0 && ADP.TimerRemaining(commandTimeoutExpiration) < ADP.TimerFromSeconds(ConnectRetryInterval))

src/Microsoft.Data.SqlClient/netfx/src/Microsoft/Data/SqlClient/SqlConnection.cs

@@ -1728,6 +1728,12 @@ private async Task ReconnectAsync(int timeout)
                         if (attempt == retryCount - 1)
                         {
                             SqlClientEventSource.Log.TryTraceEvent("<sc.SqlConnection.ReconnectAsync|INFO> Original ClientConnectionID {0} - give up reconnection", _originalConnectionId);
+                            if (e.Class >= TdsEnums.FATAL_ERROR_CLASS)
+                            {
+                                SqlClientEventSource.Log.TryTraceEvent("<sc.SqlConnection.ReconnectAsync|INFO> Original ClientConnectionID {0} - Fatal Error occured. Error Class: {1}", _originalConnectionId, e.Class);
+                                // Error Class: 20-25, usually terminates the database connection
+                                InnerConnection.CloseConnection(InnerConnection.Owner, ConnectionFactory);
+                            }
                             throw SQL.CR_AllAttemptsFailed(e, _originalConnectionId);
                         }
                         if (timeout > 0 && ADP.TimerRemaining(commandTimeoutExpiration) < ADP.TimerFromSeconds(ConnectRetryInterval))

src/Microsoft.Data.SqlClient/tests/ManualTests/SQL/ExceptionTest/ConnectionExceptionTest.cs

@@ -18,6 +18,38 @@ public class ConnectionExceptionTest
         private const string execReaderFailedMessage = "ExecuteReader requires an open and available Connection. The connection's current state is closed.";
         private const string orderIdQuery = "select orderid from orders where orderid < 10250";
 
+        [Fact]
+        public void TestConnectionStateWithErrorClass20()
+        {
+            using TestTdsServer server = TestTdsServer.StartTestServer();
+            using SqlConnection conn = new(server.ConnectionString);
+
+            conn.Open();
+            SqlCommand cmd = conn.CreateCommand();
+            cmd.CommandText = "SELECT 1";
+            int result = cmd.ExecuteNonQuery();
+
+            Assert.Equal(-1, result);
+            Assert.Equal(System.Data.ConnectionState.Open, conn.State);
+
+            server.Dispose();
+            try
+            {
+                int result2 = cmd.ExecuteNonQuery();
+            }
+            catch (SqlException ex)
+            {
+                Assert.Equal(11, ex.Class);
+                Assert.NotNull(ex.InnerException);
+                SqlException innerEx = Assert.IsType<SqlException>(ex.InnerException);
+                Assert.Equal(20, innerEx.Class);
+                Assert.StartsWith("A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible.", innerEx.Message);
+                // Since the server is not accessible driver can close the close the connection
+                // It is user responsibilty to maintain the connection.
+                Assert.Equal(System.Data.ConnectionState.Closed, conn.State);
+            }
+        }
+
         [Fact]
         public void ExceptionTests()
         {