fix pending read counters

force process sni compatibility mode by default

Author: Wraith2

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/LocalAppContextSwitches.cs

@@ -78,13 +78,13 @@ public static bool UseCompatibilityProcessSni
             {
                 if (s_useCompatibilityProcessSni == Tristate.NotInitialized)
                 {
-                    if (AppContext.TryGetSwitch(UseCompatibilityProcessSniString, out bool returnedValue) && returnedValue)
+                    if (AppContext.TryGetSwitch(UseCompatibilityProcessSniString, out bool returnedValue) && !returnedValue)
                     {
-                        s_useCompatibilityProcessSni = Tristate.True;
+                        s_useCompatibilityProcessSni = Tristate.False;
                     }
                     else
                     {
-                        s_useCompatibilityProcessSni = Tristate.False;
+                        s_useCompatibilityProcessSni = Tristate.True;
                     }
                 }
                 return s_useCompatibilityProcessSni == Tristate.True;

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/TdsParserStateObject.cs

@@ -3207,7 +3207,13 @@ internal void ReadSni(TaskCompletionSource<object> completion)
                             }
                         }
                         else
-                        {
+                        {   
+                            // this call to IncrementPendingCallbacks is required for balance
+                            // the _pendingCallbacks counter will be unconditionally decremented in ReadAsyncCallback
+                            //  so we must make sure that even though we are not making a network call that we do
+                            //  not cause an incorrect decrement which will cause disconnection from the native
+                            //  component
+                            IncrementPendingCallbacks();
                             readPacket = default;
                             error = TdsEnums.SNI_SUCCESS;
                         }