Pinning to net-9 and cleaning up older .net code path

Microsoft.Azure.Cosmos.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 16
-VisualStudioVersion = 16.0.29123.88
+# Visual Studio Version 17
+VisualStudioVersion = 17.14.36301.6 d17.14
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.Azure.Cosmos", "Microsoft.Azure.Cosmos\src\Microsoft.Azure.Cosmos.csproj", "{36F6F6A8-CEC8-4261-9948-903495BC3C25}"
 EndProject
@@ -180,6 +180,18 @@ Global
 		{021DDC27-02EF-42C4-9A9E-AA600833C2EE}.Release|Any CPU.Build.0 = Release|Any CPU
 		{021DDC27-02EF-42C4-9A9E-AA600833C2EE}.Release|x64.ActiveCfg = Release|Any CPU
 		{021DDC27-02EF-42C4-9A9E-AA600833C2EE}.Release|x64.Build.0 = Release|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Cover|Any CPU.ActiveCfg = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Cover|Any CPU.Build.0 = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Cover|x64.ActiveCfg = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Cover|x64.Build.0 = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Debug|x64.Build.0 = Debug|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Release|x64.ActiveCfg = Release|Any CPU
+		{D744906A-1091-403F-B0B6-794DE045169A}.Release|x64.Build.0 = Release|Any CPU
 		{CE4D6DA8-148D-4A98-943B-D8C2D532E1DC}.Cover|Any CPU.ActiveCfg = Debug|Any CPU
 		{CE4D6DA8-148D-4A98-943B-D8C2D532E1DC}.Cover|Any CPU.Build.0 = Debug|Any CPU
 		{CE4D6DA8-148D-4A98-943B-D8C2D532E1DC}.Cover|x64.ActiveCfg = Debug|Any CPU

Microsoft.Azure.Cosmos/FaultInjection/src/FaultInjection.csproj

@@ -8,7 +8,7 @@
 		<NeutralLanguage>en-US</NeutralLanguage>
 		<CurrentDate>$([System.DateTime]::Now.ToString(yyyyMMdd))</CurrentDate>
 		<OutputType>Exe</OutputType>
-		<TargetFramework>net6</TargetFramework>
+		<TargetFramework>net9.0</TargetFramework>
 		<TargetType>library</TargetType>
 		<Authors>Microsoft</Authors>
 		<RootNamespace>Microsoft.Azure.Cosmos.FaultInjection</RootNamespace>

Microsoft.Azure.Cosmos/FaultInjection/tests/FaultInjectionTests.csproj

@@ -5,7 +5,7 @@
 	<IsTestProject>true</IsTestProject>
 	<TreatWarningsAsErrors>true</TreatWarningsAsErrors>
 	<Platform>AnyCPU</Platform>
-	<TargetFramework>net6.0</TargetFramework>
+	<TargetFramework>net9.0</TargetFramework>
 	<IsPackable>false</IsPackable>
 	<GenerateAssemblyInfo>false</GenerateAssemblyInfo>
 	<RootNamespace>Microsoft.Azure.Cosmos.FaultInjection.Tests</RootNamespace>

Microsoft.Azure.Cosmos/src/ChangeFeedProcessor/Exceptions/ChangeFeedProcessorUserException.cs

@@ -52,6 +52,7 @@ protected ChangeFeedProcessorUserException(SerializationInfo info, StreamingCont
         /// </summary>
         /// <param name="info">The SerializationInfo object that holds serialized object data for the exception being thrown.</param>
         /// <param name="context">The StreamingContext that contains contextual information about the source or destination.</param>
+        [Obsolete("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId = "SYSLIB0051", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public override void GetObjectData(SerializationInfo info, StreamingContext context)
         {
             base.GetObjectData(info, context);

Microsoft.Azure.Cosmos/src/ChangeFeedProcessor/Exceptions/FeedException.cs

@@ -57,6 +57,7 @@ protected FeedException(SerializationInfo info, StreamingContext context)
         /// </summary>
         /// <param name="info">The SerializationInfo object that holds serialized object data for the exception being thrown.</param>
         /// <param name="context">The StreamingContext that contains contextual information about the source or destination.</param>
+        [Obsolete("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId = "SYSLIB0051", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public override void GetObjectData(SerializationInfo info, StreamingContext context)
         {
             base.GetObjectData(info, context);

Microsoft.Azure.Cosmos/src/ChangeFeedProcessor/Exceptions/LeaseLostException.cs

@@ -104,6 +104,7 @@ protected LeaseLostException(SerializationInfo info, StreamingContext context)
         /// </summary>
         /// <param name="info">The SerializationInfo object that holds serialized object data for the exception being thrown.</param>
         /// <param name="context">The StreamingContext that contains contextual information about the source or destination.</param>
+        [Obsolete("This API supports obsolete formatter-based serialization. It should not be called or extended by application code.", DiagnosticId = "SYSLIB0051", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public override void GetObjectData(SerializationInfo info, StreamingContext context)
         {
             base.GetObjectData(info, context);

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosArray.cs

@@ -42,10 +42,15 @@ protected CosmosArray()
 
         public override TResult Accept<TArg, TResult>(ICosmosElementVisitor<TArg, TResult> cosmosElementVisitor, TArg input) => cosmosElementVisitor.Visit(this, input);
 
-        public override bool Equals(CosmosElement cosmosElement) => cosmosElement is CosmosArray cosmosArray && this.Equals(cosmosArray);
+        public override bool Equals(CosmosElement? cosmosElement) => cosmosElement is CosmosArray cosmosArray && this.Equals(cosmosArray);
 
-        public bool Equals(CosmosArray cosmosArray)
+        public bool Equals(CosmosArray? cosmosArray)
         {
+            if (cosmosArray is null)
+            {
+                return false;
+            }
+
             if (this.Count != cosmosArray.Count)
             {
                 return false;
@@ -77,10 +82,15 @@ public override int GetHashCode()
             return (int)hash;
         }
 
-        public int CompareTo(CosmosArray cosmosArray)
+        public int CompareTo(CosmosArray? cosmosArray)
         {
-            UInt128 hash1 = DistinctHash.GetHash(this);
-            UInt128 hash2 = DistinctHash.GetHash(cosmosArray);
+            if (cosmosArray is null)
+            {
+                return 1;
+            }
+
+            Microsoft.Azure.Cosmos.UInt128 hash1 = DistinctHash.GetHash(this);
+            Microsoft.Azure.Cosmos.UInt128 hash2 = DistinctHash.GetHash(cosmosArray);
             return UInt128BinaryComparer.Singleton.Compare(hash1, hash2);
         }
 

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosBinary.cs

@@ -34,9 +34,15 @@ protected CosmosBinary()
 
         public override TResult Accept<TArg, TResult>(ICosmosElementVisitor<TArg, TResult> cosmosElementVisitor, TArg input) => cosmosElementVisitor.Visit(this, input);
 
-        public override bool Equals(CosmosElement cosmosElement) => cosmosElement is CosmosBinary cosmosBinary && this.Equals(cosmosBinary);
+        public override bool Equals(CosmosElement? cosmosElement)
+        {
+            return cosmosElement is CosmosBinary cosmosBinary && this.Equals(cosmosBinary);
+        }
 
-        public bool Equals(CosmosBinary cosmosBinary) => this.Value.Span.SequenceEqual(cosmosBinary.Value.Span);
+        public bool Equals(CosmosBinary? cosmosBinary)
+        {
+            return cosmosBinary is not null && this.Value.Span.SequenceEqual(cosmosBinary.Value.Span);
+        }
 
         public override int GetHashCode()
         {
@@ -45,7 +51,14 @@ public override int GetHashCode()
             return (int)hash;
         }
 
-        public int CompareTo(CosmosBinary cosmosBinary) => this.Value.Span.SequenceCompareTo(cosmosBinary.Value.Span);
+        public int CompareTo(CosmosBinary? cosmosBinary)
+        {
+            if (cosmosBinary is null)
+            {
+                return 1;
+            }
+            return this.Value.Span.SequenceCompareTo(cosmosBinary.Value.Span);
+        }
 
         public static CosmosBinary Create(
             IJsonNavigator jsonNavigator,

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosBoolean.cs

@@ -47,23 +47,27 @@ public override TResult Accept<TArg, TResult>(ICosmosElementVisitor<TArg, TResul
             return cosmosElementVisitor.Visit(this, input);
         }
 
-        public override bool Equals(CosmosElement cosmosElement)
+        public override bool Equals(CosmosElement? cosmosElement)
         {
             return cosmosElement is CosmosBoolean cosmosBoolean && this.Equals(cosmosBoolean);
-        }
+        } 
 
-        public bool Equals(CosmosBoolean cosmosBoolean)
+        public bool Equals(CosmosBoolean? cosmosBoolean)
         {
-            return this.Value == cosmosBoolean.Value;
+            return cosmosBoolean is not null && this.Value == cosmosBoolean.Value;
         }
 
         public override int GetHashCode()
         {
             return this.Value ? TrueHash : FalseHash;
         }
 
-        public int CompareTo(CosmosBoolean cosmosBoolean)
+        public int CompareTo(CosmosBoolean? cosmosBoolean)
         {
+            if (cosmosBoolean is null)
+            {
+                return 1;
+            }
             return this.Value.CompareTo(cosmosBoolean.Value);
         }
 

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosElement.cs

@@ -41,17 +41,22 @@ public override string ToString()
             return Utf8StringHelpers.ToString(jsonWriter.GetResult());
         }
 
-        public override bool Equals(object obj)
+        public override bool Equals(object? obj)
         {
             return obj is CosmosElement cosmosElement && this.Equals(cosmosElement);
         }
 
-        public abstract bool Equals(CosmosElement cosmosElement);
+        public abstract bool Equals(CosmosElement? cosmosElement);
 
         public abstract override int GetHashCode();
 
-        public int CompareTo(CosmosElement other)
+        public int CompareTo(CosmosElement? other)
         {
+            if (other is null)
+            {
+                return 1;
+            }
+
             int thisTypeOrder = this.Accept(CosmosElementToTypeOrder.Singleton);
             int otherTypeOrder = other.Accept(CosmosElementToTypeOrder.Singleton);
 

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosElementJsonConverter.cs

@@ -9,9 +9,6 @@ namespace Microsoft.Azure.Cosmos.CosmosElements
     using System;
     using System.Collections.Generic;
     using System.Linq;
-#if NETSTANDARD15 || NETSTANDARD16
-    using System.Reflection;
-#endif
     using System.Text;
     using Microsoft.Azure.Cosmos.Json.Interop;
     using Newtonsoft.Json;
@@ -77,11 +74,7 @@ sealed class CosmosElementJsonConverter : JsonConverter
 
         public override bool CanConvert(Type objectType)
         {
-#if NETSTANDARD15 || NETSTANDARD16
-            return ConvertableTypes.Contains(objectType) || ConvertableTypes.Contains(objectType.GetTypeInfo().BaseType) || objectType == typeof(CosmosElement);
-#else
             return ConvertableTypes.Contains(objectType) || ConvertableTypes.Contains(objectType.BaseType) || objectType == typeof(CosmosElement);
-#endif
         }
 
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosGuid.cs

@@ -43,14 +43,11 @@ public override TResult Accept<TArg, TResult>(ICosmosElementVisitor<TArg, TResul
             return cosmosElementVisitor.Visit(this, input);
         }
 
-        public override bool Equals(CosmosElement cosmosElement)
-        {
-            return cosmosElement is CosmosGuid cosmosGuid && this.Equals(cosmosGuid);
-        }
+        public override bool Equals(CosmosElement? cosmosElement) => cosmosElement is CosmosGuid cosmosGuid && this.Equals(cosmosGuid);
 
-        public bool Equals(CosmosGuid cosmosGuid)
+        public bool Equals(CosmosGuid? cosmosGuid)
         {
-            return this.Value == cosmosGuid.Value;
+            return cosmosGuid is not null && this.Value == cosmosGuid.Value;
         }
 
         public override int GetHashCode()
@@ -60,8 +57,12 @@ public override int GetHashCode()
             return (int)hash;
         }
 
-        public int CompareTo(CosmosGuid cosmosGuid)
+        public int CompareTo(CosmosGuid? cosmosGuid)
         {
+            if (cosmosGuid is null)
+            {
+                return 1;
+            }
             return this.Value.CompareTo(cosmosGuid.Value);
         }
 

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosNull.cs

@@ -42,14 +42,14 @@ public override TResult Accept<TArg, TResult>(ICosmosElementVisitor<TArg, TResul
             return cosmosElementVisitor.Visit(this, input);
         }
 
-        public override bool Equals(CosmosElement cosmosElement)
+        public override bool Equals(CosmosElement? cosmosElement)
         {
             return cosmosElement is CosmosNull cosmosNull && this.Equals(cosmosNull);
         }
 
-        public bool Equals(CosmosNull cosmosNull)
+        public bool Equals(CosmosNull? cosmosNull)
         {
-            return true;
+            return cosmosNull is not null;
         }
 
         public static CosmosNull Create()
@@ -91,9 +91,9 @@ public static bool TryParse(
             return CosmosElement.TryParse<CosmosNull>(json, out cosmosNull);
         }
 
-        public int CompareTo(CosmosNull other)
+        public int CompareTo(CosmosNull? other)
         {
-            return 0;
+            return other is null ? 1 : 0;
         }
 
         public static new class Monadic

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosNumber.cs

@@ -46,15 +46,20 @@ public override TResult Accept<TArg, TResult>(ICosmosElementVisitor<TArg, TResul
             return cosmosElementVisitor.Visit(this, input);
         }
 
-        public override bool Equals(CosmosElement cosmosElement)
+        public override bool Equals(CosmosElement? cosmosElement)
         {
             return cosmosElement is CosmosNumber cosmosNumber && this.Equals(cosmosNumber);
         }
 
-        public abstract bool Equals(CosmosNumber cosmosNumber);
+        public abstract bool Equals(CosmosNumber? cosmosNumber);
 
-        public int CompareTo(CosmosNumber other)
+        public int CompareTo(CosmosNumber? other)
         {
+            if (other is null)
+            {
+                return 1;
+            }
+
             int thisTypeOrder = this.Accept(CosmosNumberToTypeOrder.Singleton);
             int otherTypeOrder = other.Accept(CosmosNumberToTypeOrder.Singleton);
 

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosObject.EagerCosmosObject.cs

@@ -28,7 +28,6 @@ public EagerCosmosObject(IReadOnlyDictionary<string, CosmosElement> dictionary)
             {
                 this.dictionary = new Dictionary<string, CosmosElement>(dictionary.ToDictionary(kvp => kvp.Key, kvp => kvp.Value));
             }
-
             public override CosmosElement this[string key] => this.dictionary[key];
 
             public override int Count => this.dictionary.Count;
@@ -41,7 +40,12 @@ public EagerCosmosObject(IReadOnlyDictionary<string, CosmosElement> dictionary)
 
             public override Enumerator GetEnumerator() => new Enumerator(this.dictionary.GetEnumerator());
 
-            public override bool TryGetValue(string key, out CosmosElement value) => this.dictionary.TryGetValue(key, out value);
+            public override bool TryGetValue(string key, out CosmosElement value)
+            {
+#pragma warning disable CS8601 // Possible null reference assignment - intentional out parameter assignment
+                return this.dictionary.TryGetValue(key, out value);
+#pragma warning restore CS8601 // Possible null reference assignment
+            }
 
             public override void WriteTo(IJsonWriter jsonWriter)
             {

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosObject.LazyCosmosObject.cs

@@ -61,7 +61,12 @@ public LazyCosmosObject(IJsonNavigator jsonNavigator, IJsonNavigatorNode jsonNav
 
             public override Enumerator GetEnumerator() => new Enumerator(this.lazyCache.Value.GetEnumerator());
 
-            public override bool TryGetValue(string key, out CosmosElement value) => this.lazyCache.Value.TryGetValue(key, out value);
+            public override bool TryGetValue(string key, out CosmosElement value)
+            {
+#pragma warning disable CS8601 // Possible null reference assignment - intentional out parameter assignment
+                return this.lazyCache.Value.TryGetValue(key, out value);
+#pragma warning restore CS8601 // Possible null reference assignment
+            }
 
             public override void WriteTo(IJsonWriter jsonWriter)
             {

Microsoft.Azure.Cosmos/src/CosmosElements/CosmosObject.cs

@@ -90,19 +90,24 @@ public bool TryGetValue<TCosmosElement>(string key, out TCosmosElement typedCosm
 
         IEnumerator<KeyValuePair<string, CosmosElement>> IEnumerable<KeyValuePair<string, CosmosElement>>.GetEnumerator() => this.GetEnumerator();
 
-        public override bool Equals(CosmosElement cosmosElement)
+        public override bool Equals(CosmosElement? cosmosElement)
         {
             return cosmosElement is CosmosObject cosmosObject && this.Equals(cosmosObject);
         }
 
-        public bool Equals(CosmosObject cosmosObject)
+        public bool Equals(CosmosObject? cosmosObject)
         {
+            if (cosmosObject is null)
+            {
+                return false;
+            }
+
             if (this.Count != cosmosObject.Count)
             {
                 return false;
             }
 
-            // Order of properties does not mattter
+            // Order of properties does not matter
             foreach (KeyValuePair<string, CosmosElement> kvp in this)
             {
                 string propertyName = kvp.Key;
@@ -143,10 +148,15 @@ public override int GetHashCode()
             return (int)hash;
         }
 
-        public int CompareTo(CosmosObject cosmosObject)
+        public int CompareTo(CosmosObject? cosmosObject)
         {
-            UInt128 hash1 = DistinctHash.GetHash(this);
-            UInt128 hash2 = DistinctHash.GetHash(cosmosObject);
+            if (cosmosObject is null)
+            {
+                return 1;
+            }
+
+            Microsoft.Azure.Cosmos.UInt128 hash1 = DistinctHash.GetHash(this);
+            Microsoft.Azure.Cosmos.UInt128 hash2 = DistinctHash.GetHash(cosmosObject);
             return UInt128BinaryComparer.Singleton.Compare(hash1, hash2);
         }