diff --git a/DnsServerCore/Zone.cs b/DnsServerCore/Zone.cs
index 31935787..f1a69876 100644
--- a/DnsServerCore/Zone.cs
+++ b/DnsServerCore/Zone.cs
@@ -77,15 +77,15 @@ namespace DnsServerCore
             {
                 nsRecords.Add(new DnsResourceRecord("", DnsResourceRecordType.NS, DnsClass.IN, 172800, new DnsNSRecord(rootNameServer.Domain)));
 
-                CreateZone(this, rootNameServer.Domain).SetRecord(DnsResourceRecordType.A, new DnsResourceRecord[] { new DnsResourceRecord(rootNameServer.Domain, DnsResourceRecordType.A, DnsClass.IN, 172800, new DnsARecord(rootNameServer.EndPoint.Address)) });
+                CreateZone(this, rootNameServer.Domain).SetRecords(DnsResourceRecordType.A, new DnsResourceRecord[] { new DnsResourceRecord(rootNameServer.Domain, DnsResourceRecordType.A, DnsClass.IN, 172800, new DnsARecord(rootNameServer.EndPoint.Address)) });
             }
 
             foreach (NameServerAddress rootNameServer in DnsClient.ROOT_NAME_SERVERS_IPv6)
             {
-                CreateZone(this, rootNameServer.Domain).SetRecord(DnsResourceRecordType.AAAA, new DnsResourceRecord[] { new DnsResourceRecord(rootNameServer.Domain, DnsResourceRecordType.AAAA, DnsClass.IN, 172800, new DnsARecord(rootNameServer.EndPoint.Address)) });
+                CreateZone(this, rootNameServer.Domain).SetRecords(DnsResourceRecordType.AAAA, new DnsResourceRecord[] { new DnsResourceRecord(rootNameServer.Domain, DnsResourceRecordType.AAAA, DnsClass.IN, 172800, new DnsAAAARecord(rootNameServer.EndPoint.Address)) });
             }
 
-            SetRecord(DnsResourceRecordType.NS, nsRecords.ToArray());
+            SetRecords(DnsResourceRecordType.NS, nsRecords.ToArray());
         }
 
         private static string[] ConvertDomainToPath(string domainName)
@@ -169,9 +169,9 @@ namespace DnsServerCore
             return null;
         }
 
-        private void SetRecord(DnsResourceRecordType type, DnsResourceRecord[] records)
+        private void SetRecords(DnsResourceRecordType type, DnsResourceRecord[] records)
         {
-            DnsResourceRecord[] existingRecords = _entries.GetOrAdd(type, delegate (DnsResourceRecordType key)
+            DnsResourceRecord[] existingRecords = _entries.AddOrUpdate(type, records, delegate (DnsResourceRecordType key, DnsResourceRecord[] oldValue)
             {
                 return records;
             });
@@ -367,6 +367,42 @@ namespace DnsServerCore
 
         #region internal
 
+        internal static Dictionary<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>> GroupRecords(ICollection<DnsResourceRecord> records)
+        {
+            Dictionary<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>> groupedByDomainRecords = new Dictionary<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>>();
+
+            foreach (DnsResourceRecord record in records)
+            {
+                Dictionary<DnsResourceRecordType, List<DnsResourceRecord>> groupedByTypeRecords;
+
+                if (groupedByDomainRecords.ContainsKey(record.Name))
+                {
+                    groupedByTypeRecords = groupedByDomainRecords[record.Name];
+                }
+                else
+                {
+                    groupedByTypeRecords = new Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>();
+                    groupedByDomainRecords.Add(record.Name, groupedByTypeRecords);
+                }
+
+                List<DnsResourceRecord> groupedRecords;
+
+                if (groupedByTypeRecords.ContainsKey(record.Type))
+                {
+                    groupedRecords = groupedByTypeRecords[record.Type];
+                }
+                else
+                {
+                    groupedRecords = new List<DnsResourceRecord>();
+                    groupedByTypeRecords.Add(record.Type, groupedRecords);
+                }
+
+                groupedRecords.Add(record);
+            }
+
+            return groupedByDomainRecords;
+        }
+
         internal DnsDatagram Query(DnsDatagram request)
         {
             if (_authoritativeZone)
@@ -396,7 +432,7 @@ namespace DnsServerCore
                                 DnsResourceRecord record = new DnsResourceRecord(question.Name, question.Type, DnsClass.IN, DEFAULT_RECORD_TTL, new DnsNXRecord(authority));
                                 record.SetExpiry();
 
-                                CreateZone(this, question.Name).SetRecord(question.Type, new DnsResourceRecord[] { record });
+                                CreateZone(this, question.Name).SetRecords(question.Type, new DnsResourceRecord[] { record });
                             }
                         }
                     }
@@ -413,7 +449,7 @@ namespace DnsServerCore
                                 DnsResourceRecord record = new DnsResourceRecord(question.Name, question.Type, DnsClass.IN, DEFAULT_RECORD_TTL, new DnsEmptyRecord(authority));
                                 record.SetExpiry();
 
-                                CreateZone(this, question.Name).SetRecord(question.Type, new DnsResourceRecord[] { record });
+                                CreateZone(this, question.Name).SetRecords(question.Type, new DnsResourceRecord[] { record });
                             }
                         }
                     }
@@ -431,78 +467,51 @@ namespace DnsServerCore
             allRecords.AddRange(response.Authority);
             allRecords.AddRange(response.Additional);
 
-            #region group all records by domain and type
-
-            Dictionary<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>> cacheEntries = new Dictionary<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>>();
-
+            //set expiry for cached records
             foreach (DnsResourceRecord record in allRecords)
-            {
-                Dictionary<DnsResourceRecordType, List<DnsResourceRecord>> cacheTypeEntries;
+                record.SetExpiry();
 
-                if (cacheEntries.ContainsKey(record.Name))
-                {
-                    cacheTypeEntries = cacheEntries[record.Name];
-                }
-                else
-                {
-                    cacheTypeEntries = new Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>();
-                    cacheEntries.Add(record.Name, cacheTypeEntries);
-                }
-
-                List<DnsResourceRecord> cacheRREntries;
-
-                if (cacheTypeEntries.ContainsKey(record.Type))
-                {
-                    cacheRREntries = cacheTypeEntries[record.Type];
-                }
-                else
-                {
-                    cacheRREntries = new List<DnsResourceRecord>();
-                    cacheTypeEntries.Add(record.Type, cacheRREntries);
-                }
-
-                cacheRREntries.Add(record);
-            }
-
-            #endregion
-
-            //add grouped entries into cache
-            foreach (KeyValuePair<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>> cacheEntry in cacheEntries)
-            {
-                string domain = cacheEntry.Key;
-
-                foreach (KeyValuePair<DnsResourceRecordType, List<DnsResourceRecord>> cacheTypeEntry in cacheEntry.Value)
-                {
-                    DnsResourceRecordType type = cacheTypeEntry.Key;
-                    DnsResourceRecord[] records = cacheTypeEntry.Value.ToArray();
-
-                    foreach (DnsResourceRecord record in records)
-                        record.SetExpiry();
-
-                    CreateZone(this, domain).SetRecord(type, records);
-                }
-            }
+            SetRecords(allRecords);
 
             //cache for ANY request
             if (response.Question[0].Type == DnsResourceRecordType.ANY)
-                CreateZone(this, response.Question[0].Name).SetRecord(DnsResourceRecordType.ANY, response.Answer);
+                CreateZone(this, response.Question[0].Name).SetRecords(DnsResourceRecordType.ANY, response.Answer);
         }
 
         #endregion
 
         #region public
 
-        public void SetRecord(string domain, DnsResourceRecordType type, uint ttl, DnsResourceRecordData[] records)
+        public void SetRecords(string domain, DnsResourceRecordType type, uint ttl, DnsResourceRecordData[] records)
         {
             DnsResourceRecord[] resourceRecords = new DnsResourceRecord[records.Length];
 
             for (int i = 0; i < records.Length; i++)
                 resourceRecords[i] = new DnsResourceRecord(domain, type, DnsClass.IN, ttl, records[i]);
 
-            CreateZone(this, domain).SetRecord(type, resourceRecords);
+            CreateZone(this, domain).SetRecords(type, resourceRecords);
         }
 
-        public DnsResourceRecord[] GetAllRecords(string domain = "")
+        public void SetRecords(ICollection<DnsResourceRecord> records)
+        {
+            Dictionary<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>> groupedByDomainRecords = GroupRecords(records);
+
+            //add grouped records
+            foreach (KeyValuePair<string, Dictionary<DnsResourceRecordType, List<DnsResourceRecord>>> groupedByTypeRecords in groupedByDomainRecords)
+            {
+                string domain = groupedByTypeRecords.Key;
+
+                foreach (KeyValuePair<DnsResourceRecordType, List<DnsResourceRecord>> groupedRecords in groupedByTypeRecords.Value)
+                {
+                    DnsResourceRecordType type = groupedRecords.Key;
+                    DnsResourceRecord[] resourceRecords = groupedRecords.Value.ToArray();
+
+                    CreateZone(this, domain).SetRecords(type, resourceRecords);
+                }
+            }
+        }
+
+        public DnsResourceRecord[] GetRecords(string domain = "")
         {
             Zone currentZone = this;
 
@@ -518,7 +527,11 @@ namespace DnsServerCore
                     return new DnsResourceRecord[] { }; //no zone for given domain
             }
 
-            return currentZone.GetRecords(DnsResourceRecordType.ANY);
+            DnsResourceRecord[] records = currentZone.GetRecords(DnsResourceRecordType.ANY);
+            if (records != null)
+                return records;
+
+            return new DnsResourceRecord[] { };
         }
 
         public string[] ListSubZones(string domain = "")
@@ -543,7 +556,7 @@ namespace DnsServerCore
             return subZoneNames;
         }
 
-        public string[] ListAllAuthoritativeZones(string domain = "")
+        public string[] ListAuthoritativeZones(string domain = "")
         {
             Zone currentZone = this;
 
@@ -570,6 +583,11 @@ namespace DnsServerCore
             return zoneNames.ToArray();
         }
 
+        public bool DeleteZone(string domain)
+        {
+            return (DeleteZone(this, domain) != null);
+        }
+
         #endregion
 
         class DnsNXRecord : DnsResourceRecordData