diff --git a/src/NuGet.Core/NuGet.Protocol/HttpSourceCacheContext.cs b/src/NuGet.Core/NuGet.Protocol/HttpSourceCacheContext.cs
index 97fb1f4ab23..9bb9c2cc6b1 100644
--- a/src/NuGet.Core/NuGet.Protocol/HttpSourceCacheContext.cs
+++ b/src/NuGet.Core/NuGet.Protocol/HttpSourceCacheContext.cs
@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable disable
-
 using System;
 using System.Diagnostics;
 
@@ -10,7 +8,7 @@ namespace NuGet.Protocol.Core.Types
 {
     public class HttpSourceCacheContext
     {
-        private HttpSourceCacheContext(string rootTempFolder, TimeSpan maxAge, bool directDownload, SourceCacheContext cacheContext)
+        private HttpSourceCacheContext(string? rootTempFolder, TimeSpan maxAge, bool directDownload, SourceCacheContext cacheContext)
         {
             if (maxAge <= TimeSpan.Zero)
             {
@@ -40,7 +38,7 @@ private HttpSourceCacheContext(string rootTempFolder, TimeSpan maxAge, bool dire
         /// A suggested root folder to drop temporary files under, it will get cleared by the
         /// disposal of the <see cref="SourceCacheContext"/> that was used to create this instance.
         /// </summary>
-        public string RootTempFolder { get; }
+        public string? RootTempFolder { get; }
 
         /// <summary>
         /// Inner cache context.
diff --git a/src/NuGet.Core/NuGet.Protocol/NullSourceCacheContext.cs b/src/NuGet.Core/NuGet.Protocol/NullSourceCacheContext.cs
index 280adade61f..40e3de1378c 100644
--- a/src/NuGet.Core/NuGet.Protocol/NullSourceCacheContext.cs
+++ b/src/NuGet.Core/NuGet.Protocol/NullSourceCacheContext.cs
@@ -1,10 +1,8 @@
-#nullable disable
-
 namespace NuGet.Protocol.Core.Types
 {
     public class NullSourceCacheContext : SourceCacheContext
     {
-        private static SourceCacheContext _instance;
+        private static SourceCacheContext? _instance;
 
         public static SourceCacheContext Instance
         {
@@ -28,8 +26,8 @@ public override string GeneratedTempFolder
             }
         }
 
-        public override SourceCacheContext WithRefreshCacheTrue() { return _instance; }
+        public override SourceCacheContext WithRefreshCacheTrue() { return Instance; }
 
-        public override SourceCacheContext Clone() { return _instance; }
+        public override SourceCacheContext Clone() { return Instance; }
     }
 }
diff --git a/src/NuGet.Core/NuGet.Protocol/PackageDownloadContext.cs b/src/NuGet.Core/NuGet.Protocol/PackageDownloadContext.cs
index bff25b24e37..59590c0c8d8 100644
--- a/src/NuGet.Core/NuGet.Protocol/PackageDownloadContext.cs
+++ b/src/NuGet.Core/NuGet.Protocol/PackageDownloadContext.cs
@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable disable
-
 using System;
 using NuGet.Configuration;
 using NuGet.Packaging.Signing;
@@ -21,7 +19,7 @@ public PackageDownloadContext(SourceCacheContext sourceCacheContext) : this(
 
         public PackageDownloadContext(
             SourceCacheContext sourceCacheContext,
-            string directDownloadDirectory,
+            string? directDownloadDirectory,
             bool directDownload)
         {
             if (sourceCacheContext == null)
@@ -43,9 +41,9 @@ public PackageDownloadContext(
 
         public PackageDownloadContext(
             SourceCacheContext sourceCacheContext,
-            string directDownloadDirectory,
+            string? directDownloadDirectory,
             bool directDownload,
-            PackageSourceMapping packageSourceMappingConfiguration) : this(
+            PackageSourceMapping? packageSourceMappingConfiguration) : this(
             sourceCacheContext,
             directDownloadDirectory,
             directDownload)
@@ -55,11 +53,11 @@ public PackageDownloadContext(
 
         public SourceCacheContext SourceCacheContext { get; }
         public bool DirectDownload { get; }
-        public string DirectDownloadDirectory { get; }
+        public string? DirectDownloadDirectory { get; }
 
         public Guid ParentId { get; set; }
 
-        public ClientPolicyContext ClientPolicyContext { get; set; }
-        public PackageSourceMapping PackageSourceMapping { get; }
+        public ClientPolicyContext? ClientPolicyContext { get; set; }
+        public PackageSourceMapping? PackageSourceMapping { get; }
     }
 }
diff --git a/src/NuGet.Core/NuGet.Protocol/PublicAPI/net472/PublicAPI.Shipped.txt b/src/NuGet.Core/NuGet.Protocol/PublicAPI/net472/PublicAPI.Shipped.txt
index 1bd269ca3f7..ea7a6b20f82 100644
--- a/src/NuGet.Core/NuGet.Protocol/PublicAPI/net472/PublicAPI.Shipped.txt
+++ b/src/NuGet.Core/NuGet.Protocol/PublicAPI/net472/PublicAPI.Shipped.txt
@@ -65,8 +65,8 @@ NuGet.Protocol.Core.Types.HttpHandlerResource.HttpHandlerResource() -> void
 NuGet.Protocol.Core.Types.HttpSourceCacheContext
 NuGet.Protocol.Core.Types.HttpSourceCacheContext.DirectDownload.get -> bool
 NuGet.Protocol.Core.Types.HttpSourceCacheContext.MaxAge.get -> System.TimeSpan
-~NuGet.Protocol.Core.Types.HttpSourceCacheContext.RootTempFolder.get -> string
-~NuGet.Protocol.Core.Types.HttpSourceCacheContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext
+NuGet.Protocol.Core.Types.HttpSourceCacheContext.RootTempFolder.get -> string?
+NuGet.Protocol.Core.Types.HttpSourceCacheContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext!
 NuGet.Protocol.Core.Types.ILegacyFeedCapabilityResource
 NuGet.Protocol.Core.Types.ILegacyFeedCapabilityResource.SupportsIsAbsoluteLatestVersionAsync(NuGet.Common.ILogger! log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<bool>!
 NuGet.Protocol.Core.Types.ILegacyFeedCapabilityResource.SupportsSearchAsync(NuGet.Common.ILogger! log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<bool>!
@@ -138,17 +138,17 @@ NuGet.Protocol.Core.Types.OfflineFeedAddContext.ThrowIfPackageExistsAndInvalid.g
 NuGet.Protocol.Core.Types.OfflineFeedAddContext.ThrowIfSourcePackageIsInvalid.get -> bool
 NuGet.Protocol.Core.Types.OfflineFeedUtility
 NuGet.Protocol.Core.Types.PackageDownloadContext
-~NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.get -> NuGet.Packaging.Signing.ClientPolicyContext
-~NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.set -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.get -> NuGet.Packaging.Signing.ClientPolicyContext?
+NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.set -> void
 NuGet.Protocol.Core.Types.PackageDownloadContext.DirectDownload.get -> bool
-~NuGet.Protocol.Core.Types.PackageDownloadContext.DirectDownloadDirectory.get -> string
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext) -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, string directDownloadDirectory, bool directDownload) -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, string directDownloadDirectory, bool directDownload, NuGet.Configuration.PackageSourceMapping packageSourceMappingConfiguration) -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageSourceMapping.get -> NuGet.Configuration.PackageSourceMapping
+NuGet.Protocol.Core.Types.PackageDownloadContext.DirectDownloadDirectory.get -> string?
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext! sourceCacheContext) -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext! sourceCacheContext, string? directDownloadDirectory, bool directDownload) -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext! sourceCacheContext, string? directDownloadDirectory, bool directDownload, NuGet.Configuration.PackageSourceMapping? packageSourceMappingConfiguration) -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageSourceMapping.get -> NuGet.Configuration.PackageSourceMapping?
 NuGet.Protocol.Core.Types.PackageDownloadContext.ParentId.get -> System.Guid
 NuGet.Protocol.Core.Types.PackageDownloadContext.ParentId.set -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext
+NuGet.Protocol.Core.Types.PackageDownloadContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext!
 NuGet.Protocol.Core.Types.PackageMetadataResource
 NuGet.Protocol.Core.Types.PackageMetadataResource.PackageMetadataResource() -> void
 NuGet.Protocol.Core.Types.PackageProgressEventArgs
@@ -241,13 +241,13 @@ NuGet.Protocol.Core.Types.PluginResourceProvider
 NuGet.Protocol.Core.Types.PluginResourceProvider.PluginResourceProvider() -> void
 ~NuGet.Protocol.Core.Types.PluginResourceProvider.PluginResourceProvider(NuGet.Protocol.Plugins.IPluginManager pluginManager) -> void
 NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.get -> string
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.set -> void
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.DependencyGroups.get -> System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup>
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo other) -> bool
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Identity.get -> NuGet.Packaging.Core.PackageIdentity
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.get -> string!
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.set -> void
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.DependencyGroups.get -> System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup!>!
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo? other) -> bool
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Identity.get -> NuGet.Packaging.Core.PackageIdentity!
 NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Listed.get -> bool
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.RemoteSourceDependencyInfo(NuGet.Packaging.Core.PackageIdentity identity, bool listed, System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup> dependencyGroups, string contentUri) -> void
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.RemoteSourceDependencyInfo(NuGet.Packaging.Core.PackageIdentity! identity, bool listed, System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup!>! dependencyGroups, string! contentUri) -> void
 NuGet.Protocol.Core.Types.Repository
 NuGet.Protocol.Core.Types.Repository.ProviderFactory
 NuGet.Protocol.Core.Types.Repository.ProviderFactory.ProviderFactory() -> void
@@ -297,13 +297,13 @@ NuGet.Protocol.Core.Types.SourceCacheContext.SessionId.get -> System.Guid
 NuGet.Protocol.Core.Types.SourceCacheContext.SessionId.set -> void
 NuGet.Protocol.Core.Types.SourceCacheContext.SourceCacheContext() -> void
 NuGet.Protocol.Core.Types.SourcePackageDependencyInfo
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.DownloadUri.get -> System.Uri
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.DownloadUri.get -> System.Uri?
 NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.Listed.get -> bool
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.PackageHash.get -> string
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.Source.get -> NuGet.Protocol.Core.Types.SourceRepository
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(NuGet.Packaging.Core.PackageIdentity identity, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency> dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository source, System.Uri downloadUri, string packageHash) -> void
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string id, NuGet.Versioning.NuGetVersion version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency> dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository source) -> void
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string id, NuGet.Versioning.NuGetVersion version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency> dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository source, System.Uri downloadUri, string packageHash) -> void
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.PackageHash.get -> string?
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.Source.get -> NuGet.Protocol.Core.Types.SourceRepository?
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(NuGet.Packaging.Core.PackageIdentity! identity, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency!>! dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository? source, System.Uri? downloadUri, string? packageHash) -> void
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string! id, NuGet.Versioning.NuGetVersion! version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency!>! dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository? source) -> void
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string! id, NuGet.Versioning.NuGetVersion! version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency!>! dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository? source, System.Uri? downloadUri, string? packageHash) -> void
 NuGet.Protocol.Core.Types.SourceRepository
 NuGet.Protocol.Core.Types.SourceRepository.FeedTypeOverride.get -> NuGet.Protocol.FeedType
 NuGet.Protocol.Core.Types.SourceRepository.SourceRepository() -> void
@@ -322,11 +322,11 @@ NuGet.Protocol.Core.Types.SymbolPackageUpdateResourceV3
 ~NuGet.Protocol.Core.Types.SymbolPackageUpdateResourceV3.SymbolPackageUpdateResourceV3(string source, NuGet.Protocol.HttpSource httpSource) -> void
 NuGet.Protocol.Core.Types.UserAgent
 NuGet.Protocol.Core.Types.UserAgentStringBuilder
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.Build() -> string
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.NuGetClientVersion.get -> string
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.Build() -> string!
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.NuGetClientVersion.get -> string!
 NuGet.Protocol.Core.Types.UserAgentStringBuilder.UserAgentStringBuilder() -> void
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.UserAgentStringBuilder(string clientName) -> void
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.WithVisualStudioSKU(string vsInfo) -> NuGet.Protocol.Core.Types.UserAgentStringBuilder
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.UserAgentStringBuilder(string! clientName) -> void
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.WithVisualStudioSKU(string? vsInfo) -> NuGet.Protocol.Core.Types.UserAgentStringBuilder!
 NuGet.Protocol.Core.Types.VersionInfo
 NuGet.Protocol.Core.Types.VersionInfo.DownloadCount.get -> long?
 NuGet.Protocol.Core.Types.VersionInfo.PackageSearchMetadata.get -> NuGet.Protocol.Core.Types.IPackageSearchMetadata?
@@ -1637,18 +1637,18 @@ const NuGet.Protocol.JsonExtensions.JsonSerializationMaxDepth = 512 -> int
 ~override NuGet.Protocol.AutoCompleteResourceV3.IdStartsWith(string packageIdPrefix, bool includePrerelease, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<string>>
 ~override NuGet.Protocol.AutoCompleteResourceV3.VersionStartsWith(string packageId, string versionPrefix, bool includePrerelease, NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<NuGet.Versioning.NuGetVersion>>
 ~override NuGet.Protocol.AutoCompleteResourceV3Provider.TryCreate(NuGet.Protocol.Core.Types.SourceRepository source, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Tuple<bool, NuGet.Protocol.Core.Types.INuGetResource>>
-~override NuGet.Protocol.Core.Types.NullSourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext
-~override NuGet.Protocol.Core.Types.NullSourceCacheContext.GeneratedTempFolder.get -> string
-~override NuGet.Protocol.Core.Types.NullSourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext
+override NuGet.Protocol.Core.Types.NullSourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext!
+override NuGet.Protocol.Core.Types.NullSourceCacheContext.GeneratedTempFolder.get -> string!
+override NuGet.Protocol.Core.Types.NullSourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext!
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.CopyNupkgToStreamAsync(string id, NuGet.Versioning.NuGetVersion version, System.IO.Stream destination, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<bool>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.DoesPackageExistAsync(string id, NuGet.Versioning.NuGetVersion version, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<bool>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.GetAllVersionsAsync(string id, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<NuGet.Versioning.NuGetVersion>>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.GetDependencyInfoAsync(string id, NuGet.Versioning.NuGetVersion version, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<NuGet.Protocol.Core.Types.FindPackageByIdDependencyInfo>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.GetPackageDownloaderAsync(NuGet.Packaging.Core.PackageIdentity packageIdentity, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<NuGet.Packaging.IPackageDownloader>
 ~override NuGet.Protocol.Core.Types.PluginResourceProvider.TryCreate(NuGet.Protocol.Core.Types.SourceRepository source, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<System.Tuple<bool, NuGet.Protocol.Core.Types.INuGetResource>>
-~override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(object obj) -> bool
+override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(object? obj) -> bool
 override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.GetHashCode() -> int
-~override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ToString() -> string
+override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ToString() -> string!
 ~override NuGet.Protocol.Core.Types.SourceRepository.ToString() -> string
 ~override NuGet.Protocol.DependencyInfoResourceV2Feed.ResolvePackage(NuGet.Packaging.Core.PackageIdentity package, NuGet.Frameworks.NuGetFramework projectFramework, NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<NuGet.Protocol.Core.Types.SourcePackageDependencyInfo>
 ~override NuGet.Protocol.DependencyInfoResourceV2Feed.ResolvePackages(string packageId, NuGet.Frameworks.NuGetFramework projectFramework, NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<NuGet.Protocol.Core.Types.SourcePackageDependencyInfo>>
@@ -1895,11 +1895,11 @@ override NuGet.Protocol.VersionRangeConverter.WriteJson(Newtonsoft.Json.JsonWrit
 ~static NuGet.Protocol.CachingUtility.ReadCacheFile(System.TimeSpan maxAge, string cacheFile) -> System.IO.Stream
 ~static NuGet.Protocol.CachingUtility.RemoveInvalidFileNameChars(string value) -> string
 ~static NuGet.Protocol.Core.Types.FindPackageByIdResource.GetDependencyInfo(NuGet.Packaging.NuspecReader reader) -> NuGet.Protocol.Core.Types.FindPackageByIdDependencyInfo
-~static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, bool isFirstAttempt) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext
-~static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, int retryCount) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext
+static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext! cacheContext, bool isFirstAttempt) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext!
+static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext! cacheContext, int retryCount) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext!
 static NuGet.Protocol.Core.Types.NuGetTestMode.Enabled.get -> bool
 static NuGet.Protocol.Core.Types.NuGetTestMode.InvokeTestFunctionAgainstTestMode<T>(System.Func<T>! function, bool testModeEnabled) -> T
-~static NuGet.Protocol.Core.Types.NullSourceCacheContext.Instance.get -> NuGet.Protocol.Core.Types.SourceCacheContext
+static NuGet.Protocol.Core.Types.NullSourceCacheContext.Instance.get -> NuGet.Protocol.Core.Types.SourceCacheContext!
 ~static NuGet.Protocol.Core.Types.OfflineFeedUtility.AddPackageToSource(NuGet.Protocol.Core.Types.OfflineFeedAddContext offlineFeedAddContext, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task
 ~static NuGet.Protocol.Core.Types.OfflineFeedUtility.GetPackageDirectory(NuGet.Packaging.Core.PackageIdentity packageIdentity, string offlineFeed) -> string
 ~static NuGet.Protocol.Core.Types.OfflineFeedUtility.PackageExists(NuGet.Packaging.Core.PackageIdentity packageIdentity, string offlineFeed, out bool isValidPackage) -> bool
@@ -1920,9 +1920,9 @@ static NuGet.Protocol.Core.Types.NuGetTestMode.InvokeTestFunctionAgainstTestMode
 ~static NuGet.Protocol.Core.Types.Repository.Factory.get -> NuGet.Protocol.Core.Types.Repository.RepositoryFactory
 ~static NuGet.Protocol.Core.Types.Repository.Provider.get -> NuGet.Protocol.Core.Types.Repository.ProviderFactory
 ~static NuGet.Protocol.Core.Types.Repository.Provider.set -> void
-~static NuGet.Protocol.Core.Types.UserAgent.SetUserAgent(System.Net.Http.HttpClient client) -> void
-~static NuGet.Protocol.Core.Types.UserAgent.SetUserAgentString(NuGet.Protocol.Core.Types.UserAgentStringBuilder builder) -> void
-~static NuGet.Protocol.Core.Types.UserAgent.UserAgentString.get -> string
+static NuGet.Protocol.Core.Types.UserAgent.SetUserAgent(System.Net.Http.HttpClient! client) -> void
+static NuGet.Protocol.Core.Types.UserAgent.SetUserAgentString(NuGet.Protocol.Core.Types.UserAgentStringBuilder! builder) -> void
+static NuGet.Protocol.Core.Types.UserAgent.UserAgentString.get -> string!
 static NuGet.Protocol.Events.ProtocolDiagnostics.HttpEvent -> NuGet.Protocol.Events.ProtocolDiagnostics.ProtocolDiagnosticHttpEventHandler
 static NuGet.Protocol.Events.ProtocolDiagnostics.NupkgCopiedEvent -> NuGet.Protocol.Events.ProtocolDiagnostics.ProtocolDiagnosticsNupkgCopiedEventHandler
 static NuGet.Protocol.Events.ProtocolDiagnostics.ResourceEvent -> NuGet.Protocol.Events.ProtocolDiagnostics.ProtocolDiagnosticResourceEventHandler
@@ -2038,7 +2038,7 @@ static NuGet.Protocol.Resources.OwnerDetailsUriTemplateResourceV3.CreateOrNull(S
 ~static NuGet.Protocol.VisualStudio.FactoryExtensionsVS.GetVisualStudio(this NuGet.Protocol.Core.Types.Repository.RepositoryFactory factory, NuGet.Configuration.PackageSource source) -> NuGet.Protocol.Core.Types.SourceRepository
 ~static NuGet.Protocol.VisualStudio.FactoryExtensionsVS.GetVisualStudio(this NuGet.Protocol.Core.Types.Repository.RepositoryFactory factory, string source) -> NuGet.Protocol.Core.Types.SourceRepository
 ~static NuGet.Repositories.NuGetv3LocalRepositoryUtility.GetPackage(System.Collections.Generic.IReadOnlyList<NuGet.Repositories.NuGetv3LocalRepository> repositories, string id, NuGet.Versioning.NuGetVersion version) -> NuGet.Repositories.LocalPackageSourceInfo
-~static readonly NuGet.Protocol.Core.Types.UserAgentStringBuilder.DefaultNuGetClientName -> string
+static readonly NuGet.Protocol.Core.Types.UserAgentStringBuilder.DefaultNuGetClientName -> string!
 ~static readonly NuGet.Protocol.HttpRequestMessageConfiguration.Default -> NuGet.Protocol.HttpRequestMessageConfiguration
 static readonly NuGet.Protocol.HttpRetryHandlerRequest.DefaultDownloadTimeout -> System.TimeSpan
 static readonly NuGet.Protocol.HttpRetryHandlerRequest.DefaultMaxTries -> int
@@ -2088,11 +2088,11 @@ virtual NuGet.Protocol.Core.Types.ResourceProvider.After.get -> System.Collectio
 virtual NuGet.Protocol.Core.Types.ResourceProvider.Before.get -> System.Collections.Generic.IEnumerable<string!>!
 virtual NuGet.Protocol.Core.Types.ResourceProvider.Name.get -> string!
 virtual NuGet.Protocol.Core.Types.ResourceProvider.ResourceType.get -> System.Type!
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext!
 virtual NuGet.Protocol.Core.Types.SourceCacheContext.Dispose(bool disposing) -> void
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.get -> string
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.set -> void
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.get -> string!
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.set -> void
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext!
 ~virtual NuGet.Protocol.Core.Types.SourceRepository.GetFeedType(System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<NuGet.Protocol.FeedType>
 ~virtual NuGet.Protocol.Core.Types.SourceRepository.GetResource<T>() -> T
 ~virtual NuGet.Protocol.Core.Types.SourceRepository.GetResource<T>(System.Threading.CancellationToken token) -> T
diff --git a/src/NuGet.Core/NuGet.Protocol/PublicAPI/net8.0/PublicAPI.Shipped.txt b/src/NuGet.Core/NuGet.Protocol/PublicAPI/net8.0/PublicAPI.Shipped.txt
index 60dad4c68fd..cca4a5f5e10 100644
--- a/src/NuGet.Core/NuGet.Protocol/PublicAPI/net8.0/PublicAPI.Shipped.txt
+++ b/src/NuGet.Core/NuGet.Protocol/PublicAPI/net8.0/PublicAPI.Shipped.txt
@@ -65,8 +65,8 @@ NuGet.Protocol.Core.Types.HttpHandlerResource.HttpHandlerResource() -> void
 NuGet.Protocol.Core.Types.HttpSourceCacheContext
 NuGet.Protocol.Core.Types.HttpSourceCacheContext.DirectDownload.get -> bool
 NuGet.Protocol.Core.Types.HttpSourceCacheContext.MaxAge.get -> System.TimeSpan
-~NuGet.Protocol.Core.Types.HttpSourceCacheContext.RootTempFolder.get -> string
-~NuGet.Protocol.Core.Types.HttpSourceCacheContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext
+NuGet.Protocol.Core.Types.HttpSourceCacheContext.RootTempFolder.get -> string?
+NuGet.Protocol.Core.Types.HttpSourceCacheContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext!
 NuGet.Protocol.Core.Types.ILegacyFeedCapabilityResource
 NuGet.Protocol.Core.Types.ILegacyFeedCapabilityResource.SupportsIsAbsoluteLatestVersionAsync(NuGet.Common.ILogger! log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<bool>!
 NuGet.Protocol.Core.Types.ILegacyFeedCapabilityResource.SupportsSearchAsync(NuGet.Common.ILogger! log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<bool>!
@@ -138,17 +138,17 @@ NuGet.Protocol.Core.Types.OfflineFeedAddContext.ThrowIfPackageExistsAndInvalid.g
 NuGet.Protocol.Core.Types.OfflineFeedAddContext.ThrowIfSourcePackageIsInvalid.get -> bool
 NuGet.Protocol.Core.Types.OfflineFeedUtility
 NuGet.Protocol.Core.Types.PackageDownloadContext
-~NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.get -> NuGet.Packaging.Signing.ClientPolicyContext
-~NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.set -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.get -> NuGet.Packaging.Signing.ClientPolicyContext?
+NuGet.Protocol.Core.Types.PackageDownloadContext.ClientPolicyContext.set -> void
 NuGet.Protocol.Core.Types.PackageDownloadContext.DirectDownload.get -> bool
-~NuGet.Protocol.Core.Types.PackageDownloadContext.DirectDownloadDirectory.get -> string
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext) -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, string directDownloadDirectory, bool directDownload) -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, string directDownloadDirectory, bool directDownload, NuGet.Configuration.PackageSourceMapping packageSourceMappingConfiguration) -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.PackageSourceMapping.get -> NuGet.Configuration.PackageSourceMapping
+NuGet.Protocol.Core.Types.PackageDownloadContext.DirectDownloadDirectory.get -> string?
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext! sourceCacheContext) -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext! sourceCacheContext, string? directDownloadDirectory, bool directDownload) -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageDownloadContext(NuGet.Protocol.Core.Types.SourceCacheContext! sourceCacheContext, string? directDownloadDirectory, bool directDownload, NuGet.Configuration.PackageSourceMapping? packageSourceMappingConfiguration) -> void
+NuGet.Protocol.Core.Types.PackageDownloadContext.PackageSourceMapping.get -> NuGet.Configuration.PackageSourceMapping?
 NuGet.Protocol.Core.Types.PackageDownloadContext.ParentId.get -> System.Guid
 NuGet.Protocol.Core.Types.PackageDownloadContext.ParentId.set -> void
-~NuGet.Protocol.Core.Types.PackageDownloadContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext
+NuGet.Protocol.Core.Types.PackageDownloadContext.SourceCacheContext.get -> NuGet.Protocol.Core.Types.SourceCacheContext!
 NuGet.Protocol.Core.Types.PackageMetadataResource
 NuGet.Protocol.Core.Types.PackageMetadataResource.PackageMetadataResource() -> void
 NuGet.Protocol.Core.Types.PackageProgressEventArgs
@@ -241,13 +241,13 @@ NuGet.Protocol.Core.Types.PluginResourceProvider
 NuGet.Protocol.Core.Types.PluginResourceProvider.PluginResourceProvider() -> void
 ~NuGet.Protocol.Core.Types.PluginResourceProvider.PluginResourceProvider(NuGet.Protocol.Plugins.IPluginManager pluginManager) -> void
 NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.get -> string
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.set -> void
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.DependencyGroups.get -> System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup>
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo other) -> bool
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Identity.get -> NuGet.Packaging.Core.PackageIdentity
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.get -> string!
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ContentUri.set -> void
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.DependencyGroups.get -> System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup!>!
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo? other) -> bool
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Identity.get -> NuGet.Packaging.Core.PackageIdentity!
 NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Listed.get -> bool
-~NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.RemoteSourceDependencyInfo(NuGet.Packaging.Core.PackageIdentity identity, bool listed, System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup> dependencyGroups, string contentUri) -> void
+NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.RemoteSourceDependencyInfo(NuGet.Packaging.Core.PackageIdentity! identity, bool listed, System.Collections.Generic.IEnumerable<NuGet.Packaging.PackageDependencyGroup!>! dependencyGroups, string! contentUri) -> void
 NuGet.Protocol.Core.Types.Repository
 NuGet.Protocol.Core.Types.Repository.ProviderFactory
 NuGet.Protocol.Core.Types.Repository.ProviderFactory.ProviderFactory() -> void
@@ -297,13 +297,13 @@ NuGet.Protocol.Core.Types.SourceCacheContext.SessionId.get -> System.Guid
 NuGet.Protocol.Core.Types.SourceCacheContext.SessionId.set -> void
 NuGet.Protocol.Core.Types.SourceCacheContext.SourceCacheContext() -> void
 NuGet.Protocol.Core.Types.SourcePackageDependencyInfo
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.DownloadUri.get -> System.Uri
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.DownloadUri.get -> System.Uri?
 NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.Listed.get -> bool
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.PackageHash.get -> string
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.Source.get -> NuGet.Protocol.Core.Types.SourceRepository
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(NuGet.Packaging.Core.PackageIdentity identity, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency> dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository source, System.Uri downloadUri, string packageHash) -> void
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string id, NuGet.Versioning.NuGetVersion version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency> dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository source) -> void
-~NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string id, NuGet.Versioning.NuGetVersion version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency> dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository source, System.Uri downloadUri, string packageHash) -> void
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.PackageHash.get -> string?
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.Source.get -> NuGet.Protocol.Core.Types.SourceRepository?
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(NuGet.Packaging.Core.PackageIdentity! identity, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency!>! dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository? source, System.Uri? downloadUri, string? packageHash) -> void
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string! id, NuGet.Versioning.NuGetVersion! version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency!>! dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository? source) -> void
+NuGet.Protocol.Core.Types.SourcePackageDependencyInfo.SourcePackageDependencyInfo(string! id, NuGet.Versioning.NuGetVersion! version, System.Collections.Generic.IEnumerable<NuGet.Packaging.Core.PackageDependency!>! dependencies, bool listed, NuGet.Protocol.Core.Types.SourceRepository? source, System.Uri? downloadUri, string? packageHash) -> void
 NuGet.Protocol.Core.Types.SourceRepository
 NuGet.Protocol.Core.Types.SourceRepository.FeedTypeOverride.get -> NuGet.Protocol.FeedType
 NuGet.Protocol.Core.Types.SourceRepository.SourceRepository() -> void
@@ -322,11 +322,11 @@ NuGet.Protocol.Core.Types.SymbolPackageUpdateResourceV3
 ~NuGet.Protocol.Core.Types.SymbolPackageUpdateResourceV3.SymbolPackageUpdateResourceV3(string source, NuGet.Protocol.HttpSource httpSource) -> void
 NuGet.Protocol.Core.Types.UserAgent
 NuGet.Protocol.Core.Types.UserAgentStringBuilder
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.Build() -> string
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.NuGetClientVersion.get -> string
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.Build() -> string!
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.NuGetClientVersion.get -> string!
 NuGet.Protocol.Core.Types.UserAgentStringBuilder.UserAgentStringBuilder() -> void
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.UserAgentStringBuilder(string clientName) -> void
-~NuGet.Protocol.Core.Types.UserAgentStringBuilder.WithVisualStudioSKU(string vsInfo) -> NuGet.Protocol.Core.Types.UserAgentStringBuilder
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.UserAgentStringBuilder(string! clientName) -> void
+NuGet.Protocol.Core.Types.UserAgentStringBuilder.WithVisualStudioSKU(string? vsInfo) -> NuGet.Protocol.Core.Types.UserAgentStringBuilder!
 NuGet.Protocol.Core.Types.VersionInfo
 NuGet.Protocol.Core.Types.VersionInfo.DownloadCount.get -> long?
 NuGet.Protocol.Core.Types.VersionInfo.PackageSearchMetadata.get -> NuGet.Protocol.Core.Types.IPackageSearchMetadata?
@@ -1630,18 +1630,18 @@ const NuGet.Protocol.JsonExtensions.JsonSerializationMaxDepth = 512 -> int
 ~override NuGet.Protocol.AutoCompleteResourceV3.IdStartsWith(string packageIdPrefix, bool includePrerelease, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<string>>
 ~override NuGet.Protocol.AutoCompleteResourceV3.VersionStartsWith(string packageId, string versionPrefix, bool includePrerelease, NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<NuGet.Versioning.NuGetVersion>>
 ~override NuGet.Protocol.AutoCompleteResourceV3Provider.TryCreate(NuGet.Protocol.Core.Types.SourceRepository source, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Tuple<bool, NuGet.Protocol.Core.Types.INuGetResource>>
-~override NuGet.Protocol.Core.Types.NullSourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext
-~override NuGet.Protocol.Core.Types.NullSourceCacheContext.GeneratedTempFolder.get -> string
-~override NuGet.Protocol.Core.Types.NullSourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext
+override NuGet.Protocol.Core.Types.NullSourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext!
+override NuGet.Protocol.Core.Types.NullSourceCacheContext.GeneratedTempFolder.get -> string!
+override NuGet.Protocol.Core.Types.NullSourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext!
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.CopyNupkgToStreamAsync(string id, NuGet.Versioning.NuGetVersion version, System.IO.Stream destination, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<bool>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.DoesPackageExistAsync(string id, NuGet.Versioning.NuGetVersion version, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<bool>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.GetAllVersionsAsync(string id, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<NuGet.Versioning.NuGetVersion>>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.GetDependencyInfoAsync(string id, NuGet.Versioning.NuGetVersion version, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<NuGet.Protocol.Core.Types.FindPackageByIdDependencyInfo>
 ~override NuGet.Protocol.Core.Types.PluginFindPackageByIdResource.GetPackageDownloaderAsync(NuGet.Packaging.Core.PackageIdentity packageIdentity, NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, NuGet.Common.ILogger logger, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<NuGet.Packaging.IPackageDownloader>
 ~override NuGet.Protocol.Core.Types.PluginResourceProvider.TryCreate(NuGet.Protocol.Core.Types.SourceRepository source, System.Threading.CancellationToken cancellationToken) -> System.Threading.Tasks.Task<System.Tuple<bool, NuGet.Protocol.Core.Types.INuGetResource>>
-~override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(object obj) -> bool
+override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.Equals(object? obj) -> bool
 override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.GetHashCode() -> int
-~override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ToString() -> string
+override NuGet.Protocol.Core.Types.RemoteSourceDependencyInfo.ToString() -> string!
 ~override NuGet.Protocol.Core.Types.SourceRepository.ToString() -> string
 ~override NuGet.Protocol.DependencyInfoResourceV2Feed.ResolvePackage(NuGet.Packaging.Core.PackageIdentity package, NuGet.Frameworks.NuGetFramework projectFramework, NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<NuGet.Protocol.Core.Types.SourcePackageDependencyInfo>
 ~override NuGet.Protocol.DependencyInfoResourceV2Feed.ResolvePackages(string packageId, NuGet.Frameworks.NuGetFramework projectFramework, NuGet.Protocol.Core.Types.SourceCacheContext sourceCacheContext, NuGet.Common.ILogger log, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<NuGet.Protocol.Core.Types.SourcePackageDependencyInfo>>
@@ -1885,11 +1885,11 @@ override NuGet.Protocol.VersionRangeConverter.WriteJson(Newtonsoft.Json.JsonWrit
 ~static NuGet.Protocol.CachingUtility.ReadCacheFile(System.TimeSpan maxAge, string cacheFile) -> System.IO.Stream
 ~static NuGet.Protocol.CachingUtility.RemoveInvalidFileNameChars(string value) -> string
 ~static NuGet.Protocol.Core.Types.FindPackageByIdResource.GetDependencyInfo(NuGet.Packaging.NuspecReader reader) -> NuGet.Protocol.Core.Types.FindPackageByIdDependencyInfo
-~static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, bool isFirstAttempt) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext
-~static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext cacheContext, int retryCount) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext
+static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext! cacheContext, bool isFirstAttempt) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext!
+static NuGet.Protocol.Core.Types.HttpSourceCacheContext.Create(NuGet.Protocol.Core.Types.SourceCacheContext! cacheContext, int retryCount) -> NuGet.Protocol.Core.Types.HttpSourceCacheContext!
 static NuGet.Protocol.Core.Types.NuGetTestMode.Enabled.get -> bool
 static NuGet.Protocol.Core.Types.NuGetTestMode.InvokeTestFunctionAgainstTestMode<T>(System.Func<T>! function, bool testModeEnabled) -> T
-~static NuGet.Protocol.Core.Types.NullSourceCacheContext.Instance.get -> NuGet.Protocol.Core.Types.SourceCacheContext
+static NuGet.Protocol.Core.Types.NullSourceCacheContext.Instance.get -> NuGet.Protocol.Core.Types.SourceCacheContext!
 ~static NuGet.Protocol.Core.Types.OfflineFeedUtility.AddPackageToSource(NuGet.Protocol.Core.Types.OfflineFeedAddContext offlineFeedAddContext, System.Threading.CancellationToken token) -> System.Threading.Tasks.Task
 ~static NuGet.Protocol.Core.Types.OfflineFeedUtility.GetPackageDirectory(NuGet.Packaging.Core.PackageIdentity packageIdentity, string offlineFeed) -> string
 ~static NuGet.Protocol.Core.Types.OfflineFeedUtility.PackageExists(NuGet.Packaging.Core.PackageIdentity packageIdentity, string offlineFeed, out bool isValidPackage) -> bool
@@ -1910,9 +1910,9 @@ static NuGet.Protocol.Core.Types.NuGetTestMode.InvokeTestFunctionAgainstTestMode
 ~static NuGet.Protocol.Core.Types.Repository.Factory.get -> NuGet.Protocol.Core.Types.Repository.RepositoryFactory
 ~static NuGet.Protocol.Core.Types.Repository.Provider.get -> NuGet.Protocol.Core.Types.Repository.ProviderFactory
 ~static NuGet.Protocol.Core.Types.Repository.Provider.set -> void
-~static NuGet.Protocol.Core.Types.UserAgent.SetUserAgent(System.Net.Http.HttpClient client) -> void
-~static NuGet.Protocol.Core.Types.UserAgent.SetUserAgentString(NuGet.Protocol.Core.Types.UserAgentStringBuilder builder) -> void
-~static NuGet.Protocol.Core.Types.UserAgent.UserAgentString.get -> string
+static NuGet.Protocol.Core.Types.UserAgent.SetUserAgent(System.Net.Http.HttpClient! client) -> void
+static NuGet.Protocol.Core.Types.UserAgent.SetUserAgentString(NuGet.Protocol.Core.Types.UserAgentStringBuilder! builder) -> void
+static NuGet.Protocol.Core.Types.UserAgent.UserAgentString.get -> string!
 static NuGet.Protocol.Events.ProtocolDiagnostics.HttpEvent -> NuGet.Protocol.Events.ProtocolDiagnostics.ProtocolDiagnosticHttpEventHandler
 static NuGet.Protocol.Events.ProtocolDiagnostics.NupkgCopiedEvent -> NuGet.Protocol.Events.ProtocolDiagnostics.ProtocolDiagnosticsNupkgCopiedEventHandler
 static NuGet.Protocol.Events.ProtocolDiagnostics.ResourceEvent -> NuGet.Protocol.Events.ProtocolDiagnostics.ProtocolDiagnosticResourceEventHandler
@@ -2026,7 +2026,7 @@ static NuGet.Protocol.Resources.OwnerDetailsUriTemplateResourceV3.CreateOrNull(S
 ~static NuGet.Protocol.VisualStudio.FactoryExtensionsVS.GetVisualStudio(this NuGet.Protocol.Core.Types.Repository.RepositoryFactory factory, NuGet.Configuration.PackageSource source) -> NuGet.Protocol.Core.Types.SourceRepository
 ~static NuGet.Protocol.VisualStudio.FactoryExtensionsVS.GetVisualStudio(this NuGet.Protocol.Core.Types.Repository.RepositoryFactory factory, string source) -> NuGet.Protocol.Core.Types.SourceRepository
 ~static NuGet.Repositories.NuGetv3LocalRepositoryUtility.GetPackage(System.Collections.Generic.IReadOnlyList<NuGet.Repositories.NuGetv3LocalRepository> repositories, string id, NuGet.Versioning.NuGetVersion version) -> NuGet.Repositories.LocalPackageSourceInfo
-~static readonly NuGet.Protocol.Core.Types.UserAgentStringBuilder.DefaultNuGetClientName -> string
+static readonly NuGet.Protocol.Core.Types.UserAgentStringBuilder.DefaultNuGetClientName -> string!
 ~static readonly NuGet.Protocol.HttpRequestMessageConfiguration.Default -> NuGet.Protocol.HttpRequestMessageConfiguration
 static readonly NuGet.Protocol.HttpRetryHandlerRequest.DefaultDownloadTimeout -> System.TimeSpan
 static readonly NuGet.Protocol.HttpRetryHandlerRequest.DefaultMaxTries -> int
@@ -2076,11 +2076,11 @@ virtual NuGet.Protocol.Core.Types.ResourceProvider.After.get -> System.Collectio
 virtual NuGet.Protocol.Core.Types.ResourceProvider.Before.get -> System.Collections.Generic.IEnumerable<string!>!
 virtual NuGet.Protocol.Core.Types.ResourceProvider.Name.get -> string!
 virtual NuGet.Protocol.Core.Types.ResourceProvider.ResourceType.get -> System.Type!
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.Clone() -> NuGet.Protocol.Core.Types.SourceCacheContext!
 virtual NuGet.Protocol.Core.Types.SourceCacheContext.Dispose(bool disposing) -> void
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.get -> string
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.set -> void
-~virtual NuGet.Protocol.Core.Types.SourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.get -> string!
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.GeneratedTempFolder.set -> void
+virtual NuGet.Protocol.Core.Types.SourceCacheContext.WithRefreshCacheTrue() -> NuGet.Protocol.Core.Types.SourceCacheContext!
 ~virtual NuGet.Protocol.Core.Types.SourceRepository.GetFeedType(System.Threading.CancellationToken token) -> System.Threading.Tasks.Task<NuGet.Protocol.FeedType>
 ~virtual NuGet.Protocol.Core.Types.SourceRepository.GetResource<T>() -> T
 ~virtual NuGet.Protocol.Core.Types.SourceRepository.GetResource<T>(System.Threading.CancellationToken token) -> T
diff --git a/src/NuGet.Core/NuGet.Protocol/RemoteSourceDependencyInfo.cs b/src/NuGet.Core/NuGet.Protocol/RemoteSourceDependencyInfo.cs
index 6ee08d0a0f8..7c3954c3777 100644
--- a/src/NuGet.Core/NuGet.Protocol/RemoteSourceDependencyInfo.cs
+++ b/src/NuGet.Core/NuGet.Protocol/RemoteSourceDependencyInfo.cs
@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using System.Globalization;
@@ -40,6 +38,11 @@ public RemoteSourceDependencyInfo(
                 throw new ArgumentNullException(nameof(dependencyGroups));
             }
 
+            if (contentUri == null)
+            {
+                throw new ArgumentNullException(nameof(contentUri));
+            }
+
             Identity = identity;
             Listed = listed;
             DependencyGroups = dependencyGroups.ToList();
@@ -66,7 +69,7 @@ public RemoteSourceDependencyInfo(
         /// </summary>
         public string ContentUri { get; set; }
 
-        public bool Equals(RemoteSourceDependencyInfo other)
+        public bool Equals(RemoteSourceDependencyInfo? other)
         {
             return other != null &&
                    Identity.Equals(other.Identity) &&
@@ -74,7 +77,7 @@ public bool Equals(RemoteSourceDependencyInfo other)
                    string.Equals(ContentUri, other.ContentUri, StringComparison.Ordinal);
         }
 
-        public override bool Equals(object obj) => Equals(obj as PackageDependencyInfo);
+        public override bool Equals(object? obj) => Equals(obj as RemoteSourceDependencyInfo);
 
         public override int GetHashCode()
         {
diff --git a/src/NuGet.Core/NuGet.Protocol/SourceCacheContext.cs b/src/NuGet.Core/NuGet.Protocol/SourceCacheContext.cs
index 1bbfaf7b437..09ecfa7451f 100644
--- a/src/NuGet.Core/NuGet.Protocol/SourceCacheContext.cs
+++ b/src/NuGet.Core/NuGet.Protocol/SourceCacheContext.cs
@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable disable
-
 using System;
 using System.Diagnostics;
 using System.IO;
@@ -19,7 +17,7 @@ public class SourceCacheContext : IDisposable
         /// <summary>
         /// Path of temp folder if requested by GeneratedTempFolder
         /// </summary>
-        private string _generatedTempFolder = null;
+        private string? _generatedTempFolder;
 
         /// <summary>
         /// Default amount of time to cache version lists.
@@ -121,16 +119,17 @@ public virtual string GeneratedTempFolder
         /// </summary>
         public virtual SourceCacheContext Clone()
         {
-            return new SourceCacheContext()
+            var clone = new SourceCacheContext()
             {
                 DirectDownload = DirectDownload,
                 IgnoreFailedSources = IgnoreFailedSources,
                 MaxAge = MaxAge,
                 NoCache = NoCache,
-                GeneratedTempFolder = _generatedTempFolder,
                 RefreshMemoryCache = RefreshMemoryCache,
                 SessionId = SessionId
             };
+            clone._generatedTempFolder = _generatedTempFolder;
+            return clone;
         }
 
         /// <summary>
@@ -161,7 +160,7 @@ protected virtual void Dispose(bool disposing)
             {
                 try
                 {
-                    Directory.Delete(_generatedTempFolder, recursive: true);
+                    Directory.Delete(currentTempFolder, recursive: true);
                 }
                 catch
                 {
diff --git a/src/NuGet.Core/NuGet.Protocol/SourcePackageDependencyInfo.cs b/src/NuGet.Core/NuGet.Protocol/SourcePackageDependencyInfo.cs
index 5158546f5e5..6361eda8015 100644
--- a/src/NuGet.Core/NuGet.Protocol/SourcePackageDependencyInfo.cs
+++ b/src/NuGet.Core/NuGet.Protocol/SourcePackageDependencyInfo.cs
@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable disable
-
 using System;
 using System.Collections.Generic;
 using NuGet.Packaging.Core;
@@ -17,7 +15,7 @@ public SourcePackageDependencyInfo(
             NuGetVersion version,
             IEnumerable<PackageDependency> dependencies,
             bool listed,
-            SourceRepository source)
+            SourceRepository? source)
             : this(
                   new PackageIdentity(id, version),
                   dependencies,
@@ -33,9 +31,9 @@ public SourcePackageDependencyInfo(
             NuGetVersion version,
             IEnumerable<PackageDependency> dependencies,
             bool listed,
-            SourceRepository source,
-            Uri downloadUri,
-            string packageHash)
+            SourceRepository? source,
+            Uri? downloadUri,
+            string? packageHash)
             : this(
                   new PackageIdentity(id, version),
                   dependencies,
@@ -50,9 +48,9 @@ public SourcePackageDependencyInfo(
             PackageIdentity identity,
             IEnumerable<PackageDependency> dependencies,
             bool listed,
-            SourceRepository source,
-            Uri downloadUri,
-            string packageHash)
+            SourceRepository? source,
+            Uri? downloadUri,
+            string? packageHash)
             : base(identity, dependencies)
         {
             Listed = listed;
@@ -70,18 +68,18 @@ public SourcePackageDependencyInfo(
         /// <summary>
         /// Source repository the dependency information was retrieved from.
         /// </summary>
-        public SourceRepository Source { get; }
+        public SourceRepository? Source { get; }
 
         /// <summary>
         /// The HTTP, UNC, or local file URI to the package nupkg.
         /// </summary>
         /// <remarks>Optional</remarks>
-        public Uri DownloadUri { get; }
+        public Uri? DownloadUri { get; }
 
         /// <summary>
         /// Package hash
         /// </summary>
         /// <remarks>Optional</remarks>
-        public string PackageHash { get; }
+        public string? PackageHash { get; }
     }
 }
diff --git a/src/NuGet.Core/NuGet.Protocol/UserAgent.cs b/src/NuGet.Core/NuGet.Protocol/UserAgent.cs
index 97fb8097984..ee5a27cba69 100644
--- a/src/NuGet.Core/NuGet.Protocol/UserAgent.cs
+++ b/src/NuGet.Core/NuGet.Protocol/UserAgent.cs
@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable disable
-
 using System;
 using System.Net.Http;
 using NuGet.Packaging;
diff --git a/src/NuGet.Core/NuGet.Protocol/UserAgentStringBuilder.cs b/src/NuGet.Core/NuGet.Protocol/UserAgentStringBuilder.cs
index 164834cafcf..cf82151c7b3 100644
--- a/src/NuGet.Core/NuGet.Protocol/UserAgentStringBuilder.cs
+++ b/src/NuGet.Core/NuGet.Protocol/UserAgentStringBuilder.cs
@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable disable
-
 #if NETCOREAPP
 using System;
 #endif
@@ -22,9 +20,9 @@ public class UserAgentStringBuilder
         private const string UserAgentTemplate = "{0}/{1}";
 
         private readonly string _clientName;
-        private string _vsInfo;
-        private string _osInfo;
-        private string _ciInfo;
+        private string? _vsInfo;
+        private string? _osInfo;
+        private string? _ciInfo;
 
         public UserAgentStringBuilder()
             : this(DefaultNuGetClientName)
@@ -54,7 +52,7 @@ internal UserAgentStringBuilder(string clientName, IEnvironmentVariableReader en
 
         public string NuGetClientVersion { get; }
 
-        public UserAgentStringBuilder WithVisualStudioSKU(string vsInfo)
+        public UserAgentStringBuilder WithVisualStudioSKU(string? vsInfo)
         {
             _vsInfo = vsInfo;
             return this;