Reduce the rate at which PopulateGrid is called to prevent the UI from grinding to a halt.

BulkPrinting/BulkPrinting/BatchDownloader.cs

                         Log.Error(e, "Error while downloading batch list");
                     }
 
+                    // TODO: throttle or detect changes better
                     if (!isCancelled && doRefresh)
                     {
                         doRefresh = false;
                     try
                     {
                         using (var command = _db.CreateCommand(
-                            "SELECT Id FROM Batch WHERE Downloaded=0 ORDER BY Downloaded, Id"))
+                            "SELECT Id, ReadyForDownload FROM Batch WHERE Downloaded=0 ORDER BY Downloaded, Id"))
                         {
                             using (SQLiteDataReader row = command.ExecuteReader())
                             {
                                 while (! isCancelled && row.Read())
                                 {
                                     int batchId = (int)row["Id"];
+                                    bool oldReadyForDownload = (bool)row["ReadyForDownload"];
                                     try
                                     {
                                         Batch batch = new Batch();
                                         if (Utility.RESTRequest(ref batch, String.Format("/api/batches/{0}", batchId)))
                                         {
-                                            doRefresh = true;
+                                            if (batch.ReadyForDownload != oldReadyForDownload)
+                                            {
+                                                doRefresh = true;
+                                            }
                                             Utility.SaveBatch(_db, batch);
 
                                             if (batch.ReadyForDownload)
                                                     _db.ExecuteNonQuery(
                                                         "UPDATE Batch SET Downloaded=1 WHERE Id=@BatchId",
                                                         new SQLiteParameter("@BatchId", batchId));
+
+                                                    doRefresh = true;
                                                 }
                                             }
                                         }
                                         Log.Error(e, "Error while downloading vouchers for batch {0}", batchId);
                                     }
 
+                                    /* TODO: throttle or detect changes better
                                     if (!isCancelled && doRefresh)
                                     {
                                         doRefresh = false;
                                         _refreshAction();
                                     }
+                                    */
 
                                     lock(_lock)
                                     {
                     {
                         Log.Error(e, "Error while downloading vouchers");
                     }
+
+                    // TODO: throttle or detect changes better
+                    if (!isCancelled && doRefresh)
+                    {
+                        doRefresh = false;
+                        _refreshAction();
+                    }
                 }
                 else
                 {