Even more performance optimizations

MQTTnet.Core/Packets/MqttConnAckPacket.cs

@@ -10,7 +10,7 @@ namespace MQTTnet.Core.Packets
 
         public override string ToString()
         {
-            return $"{nameof(MqttConnAckPacket)}: [ConnectReturnCode={ConnectReturnCode}] [IsSessionPresent={IsSessionPresent}]";
+            return nameof(MqttConnAckPacket) + ": [ConnectReturnCode=" + ConnectReturnCode + "] [IsSessionPresent=" + IsSessionPresent + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttConnectPacket.cs

@@ -2,7 +2,7 @@
 
 namespace MQTTnet.Core.Packets
 {
-    public sealed class MqttConnectPacket: MqttBasePacket
+    public sealed class MqttConnectPacket : MqttBasePacket
     {
         public MqttProtocolVersion ProtocolVersion { get; set; }
 
@@ -20,7 +20,7 @@ namespace MQTTnet.Core.Packets
 
         public override string ToString()
         {
-            return $"{nameof(MqttConnectPacket)} [ClientId={ClientId}] [Username={Username}] [Password={Password}] [KeepAlivePeriod={KeepAlivePeriod}] [CleanSession={CleanSession}]";
+            return nameof(MqttConnectPacket) + ": [ClientId=" + ClientId + "] [Username=" + Username + "] [Password=" + Password + "] [KeepAlivePeriod=" + KeepAlivePeriod + "] [CleanSession=" + CleanSession + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttPublishPacket.cs

@@ -1,4 +1,4 @@
-using System.Text;
+using System;
 using MQTTnet.Core.Protocol;
 
 namespace MQTTnet.Core.Packets
@@ -17,8 +17,13 @@ namespace MQTTnet.Core.Packets
 
         public override string ToString()
         {
-            return
-                $"{nameof(MqttPublishPacket)} [Topic={Topic}] [Payload={Encoding.UTF8.GetString(Payload, 0, Payload.Length)}] [QoSLevel={QualityOfServiceLevel}] [Dup={Dup}] [Retain={Retain}] [PacketIdentifier={PacketIdentifier}]";
+            return nameof(MqttPublishPacket) + 
+                ": [Topic=" + Topic + "]" +
+                " [Payload=" + Convert.ToBase64String(Payload) + "]" +
+                " [QoSLevel=" + QualityOfServiceLevel + "]" +
+                " [Dup=" + Dup + "]" +
+                " [Retain=" + Retain + "]" +
+                " [PacketIdentifier=" + PacketIdentifier + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttSubAckPacket.cs

@@ -13,8 +13,7 @@ namespace MQTTnet.Core.Packets
         public override string ToString()
         {
             var subscribeReturnCodesText = string.Join(",", SubscribeReturnCodes.Select(f => f.ToString()));
-            return
-                $"{nameof(MqttSubAckPacket)} [PacketIdentifier={PacketIdentifier}] [SubscribeReturnCodes={subscribeReturnCodesText}]";
+            return nameof(MqttSubAckPacket) + ": [PacketIdentifier=" + PacketIdentifier + "] [SubscribeReturnCodes=" + subscribeReturnCodesText + "]";
         }
     }
 }

MQTTnet.Core/Packets/MqttSubscribePacket.cs

@@ -12,8 +12,7 @@ namespace MQTTnet.Core.Packets
         public override string ToString()
         {
             var topicFiltersText = string.Join(",", TopicFilters.Select(f => $"{f.Topic}@{f.QualityOfServiceLevel}"));
-            return
-                $"{nameof(MqttSubscribePacket)} [PacketIdentifier={PacketIdentifier}] [TopicFilters={topicFiltersText}]";
+            return nameof(MqttSubscribePacket) + ": [PacketIdentifier=" + PacketIdentifier + "] [TopicFilters=" + topicFiltersText + "]";
         }
     }
 }

MQTTnet.Core/Server/MqttClientSession.cs

@@ -76,7 +76,7 @@ namespace MQTTnet.Core.Server
                 _cancellationTokenSource.Cancel();
                 Adapter = null;
 
-                MqttTrace.Information(nameof(MqttClientSession), $"Client '{_identifier}': Disconnected.");
+                MqttTrace.Information(nameof(MqttClientSession), "Client '{0}': Disconnected.", _identifier);
             }
         }