Fixed CSHARP-412. When looking for a replica set member to send slaveOk queries to it is sufficient to look for IsSecondary members. It is not necessary to check IsPassive because IsSecondary will also be true for passive members. And most importantly, IsSecondary will temporarily change to false if a passive member is in recovering mode (and IsPassive remains true), and we don't want to send slaveOk queries to passive members that are in recovering mode.

Author: rstam

Driver/Core/ConnectWaitFor.cs

@@ -34,7 +34,7 @@ public enum ConnectWaitFor
         /// </summary>
         Primary,
         /// <summary>
-        /// Wait for any slaveOk member of the replica set to be connected (includes primary, secondaries and passives).
+        /// Wait for any slaveOk member of the replica set to be connected (primary or any secondary).
         /// </summary>
         AnySlaveOk
     }

Driver/Core/MongoServer.cs

@@ -599,7 +599,8 @@ public virtual void Connect(TimeSpan timeout, ConnectWaitFor waitFor)
                                         }
                                         break;
                                     case ConnectWaitFor.AnySlaveOk:
-                                        if (_instances.Any(i => i.State == MongoServerState.Connected && (i.IsPrimary || i.IsSecondary || i.IsPassive)))
+                                        // don't check for IsPassive because IsSecondary is also true for passives (and only true if not in recovery mode)
+                                        if (_instances.Any(i => i.State == MongoServerState.Connected && (i.IsPrimary || i.IsSecondary)))
                                         {
                                             return;
                                         }
@@ -1162,7 +1163,8 @@ internal MongoServerInstance ChooseServerInstance(bool slaveOk)
                                         _loadBalancingInstanceIndex = 0;
                                     }
                                     var instance = _instances[_loadBalancingInstanceIndex];
-                                    if (instance.State == MongoServerState.Connected && (instance.IsSecondary || instance.IsPassive))
+                                    // don't check for IsPassive because IsSecondary is also true for passives (and only true if not in recovery mode)
+                                    if (instance.State == MongoServerState.Connected && instance.IsSecondary)
                                     {
                                         return instance;
                                     }

Driver/Internal/ReplicaSetConnector.cs

@@ -79,7 +79,8 @@ internal void Connect(TimeSpan timeout, ConnectWaitFor waitFor)
                         }
                         break;
                     case ConnectWaitFor.AnySlaveOk:
-                        if (_server.Instances.Any(i => (i.IsPrimary || i.IsSecondary || i.IsPassive) && i.State == MongoServerState.Connected))
+                        // don't check for IsPassive because IsSecondary is also true for passives (and only true if not in recovery mode)
+                        if (_server.Instances.Any(i => (i.IsPrimary || i.IsSecondary) && i.State == MongoServerState.Connected))
                         {
                             exitEarly = true;
                         }