Optimize DispatchProperties and ReceiveProperties storage

src/NServiceBus.AcceptanceTesting/Support/DeepCopy.cs

@@ -15,6 +15,7 @@ namespace System
     using System.ArrayExtensions;
     using System.Collections.Generic;
     using System.Reflection;
+    using System.Runtime.CompilerServices;
 
     [Diagnostics.CodeAnalysis.SuppressMessage("Code", "PS0025:Dictionary keys should implement IEquatable<T>",
         Justification = "A DeepCopy algorithm requires reference counting necessitating dictionaries keyed on objects by reference")]
@@ -123,7 +124,11 @@ public override int GetHashCode(object obj)
                 return 0;
             }
 
-            return obj.GetHashCode();
+            // RuntimeHelpers.GetHashCode returns the identity hash code, which avoids
+            // calling ValueType.GetHashCode() on structs marked with [InlineArray]
+            // (that throws NotSupportedException). This matches the BCL
+            // System.Collections.Generic.ReferenceEqualityComparer behavior.
+            return RuntimeHelpers.GetHashCode(obj);
         }
     }
 

src/NServiceBus.Core.Tests/ApprovalFiles/APIApprovals.ApproveNServiceBus.approved.txt

@@ -2451,13 +2451,26 @@ namespace NServiceBus.Transport
         Default = 1,
         Isolated = 2,
     }
-    public class DispatchProperties : System.Collections.Generic.Dictionary<string, string>
+    public class DispatchProperties : System.Collections.Generic.ICollection<System.Collections.Generic.KeyValuePair<string, string>>, System.Collections.Generic.IDictionary<string, string>, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, string>>, System.Collections.Generic.IReadOnlyCollection<System.Collections.Generic.KeyValuePair<string, string>>, System.Collections.Generic.IReadOnlyDictionary<string, string>, System.Collections.IEnumerable
     {
         public DispatchProperties() { }
         public DispatchProperties(System.Collections.Generic.Dictionary<string, string> properties) { }
-        public NServiceBus.DelayedDelivery.DelayDeliveryWith DelayDeliveryWith { get; set; }
-        public NServiceBus.Performance.TimeToBeReceived.DiscardIfNotReceivedBefore DiscardIfNotReceivedBefore { get; set; }
-        public NServiceBus.DelayedDelivery.DoNotDeliverBefore DoNotDeliverBefore { get; set; }
+        public DispatchProperties(System.Collections.Generic.IDictionary<string, string> properties) { }
+        public int Count { get; }
+        public NServiceBus.DelayedDelivery.DelayDeliveryWith? DelayDeliveryWith { get; set; }
+        public NServiceBus.Performance.TimeToBeReceived.DiscardIfNotReceivedBefore? DiscardIfNotReceivedBefore { get; set; }
+        public NServiceBus.DelayedDelivery.DoNotDeliverBefore? DoNotDeliverBefore { get; set; }
+        public bool IsReadOnly { get; }
+        public string this[string key] { get; set; }
+        public System.Collections.Generic.ICollection<string> Keys { get; }
+        public System.Collections.Generic.ICollection<string> Values { get; }
+        public void Add(string key, string value) { }
+        public void Clear() { }
+        public bool ContainsKey(string key) { }
+        public System.Collections.Generic.IEnumerator<System.Collections.Generic.KeyValuePair<string, string>> GetEnumerator() { }
+        public bool Remove(string key) { }
+        public bool TryAdd(string key, string value) { }
+        public bool TryGetValue(string key, [System.Diagnostics.CodeAnalysis.MaybeNullWhen(false)] out string value) { }
     }
     public class ErrorContext
     {

src/NServiceBus.Core.Tests/ApprovalFiles/NullableAnnotations.ApproveNullableTypes.approved.txt

@@ -66,7 +66,6 @@ NServiceBus.Settings.IReadOnlySettings
 NServiceBus.Settings.SettingsHolder
 NServiceBus.StaticHeadersConfigExtensions
 NServiceBus.SubscriptionMigrationModeSettings
-NServiceBus.Transport.DispatchProperties
 NServiceBus.Transport.ErrorContext
 NServiceBus.Transport.IMessageDispatcher
 NServiceBus.Transport.IMessageReceiver

src/NServiceBus.Core.Tests/ApprovalFiles/StructConventionsTests.ApproveStructsWhichDontFollowStructGuidelines.approved.txt

@@ -19,3 +19,21 @@ NServiceBus.Extensibility.ContextBag+Slot violates the following rules:
       - Field Value of type System.Object is a reference type.
    - The size cannot be determined because there are fields that are reference types.
 
+NServiceBus.Transport.DispatchProperties+Slot violates the following rules:
+   - The following fields are public, so the type is not immutable:
+      - Field Key of type System.String is public.
+      - Field Value of type System.String is public.
+   - The following fields are reference types, which are potentially mutable:
+      - Field Key of type System.String is a reference type.
+      - Field Value of type System.String is a reference type.
+   - The size cannot be determined because there are fields that are reference types.
+
+NServiceBus.Transport.ReceiveProperties+Slot violates the following rules:
+   - The following fields are public, so the type is not immutable:
+      - Field Key of type System.String is public.
+      - Field Value of type System.String is public.
+   - The following fields are reference types, which are potentially mutable:
+      - Field Key of type System.String is a reference type.
+      - Field Value of type System.String is a reference type.
+   - The size cannot be determined because there are fields that are reference types.
+

src/NServiceBus.Core.Tests/Transports/ReceivePropertiesTests.cs

@@ -34,7 +34,7 @@ public void Should_wrap_provided_dictionary()
     }
 
     [Test]
-    public void Should_be_same_reference_as_source()
+    public void Should_copy_from_provided_dictionary()
     {
         var source = new Dictionary<string, string> { ["Key"] = "Value" };
         var properties = new ReceiveProperties(source);

src/NServiceBus.Core/Pipeline/Incoming/TransportReceiveToPhysicalMessageConnector.cs

@@ -113,7 +113,7 @@ static TransportOperation[] ConvertToOutboxOperations(Transport.TransportOperati
         return transportOperations;
     }
 
-    static void SerializeRoutingStrategy(AddressTag addressTag, Dictionary<string, string> options)
+    static void SerializeRoutingStrategy(AddressTag addressTag, DispatchProperties options)
     {
         switch (addressTag)
         {
@@ -128,7 +128,7 @@ static void SerializeRoutingStrategy(AddressTag addressTag, Dictionary<string, s
         }
     }
 
-    static AddressTag DeserializeRoutingStrategy(Dictionary<string, string> options)
+    static AddressTag DeserializeRoutingStrategy(DispatchProperties options)
     {
         if (options.Remove("Destination", out var destination))
         {