diff --git a/build/Shared/DeconstructionExtensions.cs b/build/Shared/DeconstructionExtensions.cs
deleted file mode 100644
index 0666ea5a46f..00000000000
--- a/build/Shared/DeconstructionExtensions.cs
+++ /dev/null
@@ -1,19 +0,0 @@
-// Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. See the LICENSE.md file in the project root for more information.
-
-#if NETFRAMEWORK || NETSTANDARD2_0
-
-using System.Diagnostics;
-
-namespace System.Collections.Generic;
-
-internal static class DeconstructionExtensions
-{
-    [DebuggerStepThrough]
-    public static void Deconstruct<TKey, TValue>(this KeyValuePair<TKey, TValue> pair, out TKey key, out TValue value)
-    {
-        key = pair.Key;
-        value = pair.Value;
-    }
-}
-
-#endif
diff --git a/build/Shared/NullableAttributes.cs b/build/Shared/NullableAttributes.cs
index 6b9f9d19dbf..d2ea0000a17 100644
--- a/build/Shared/NullableAttributes.cs
+++ b/build/Shared/NullableAttributes.cs
@@ -4,11 +4,10 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#if !NETSTANDARD2_1 && !NETCOREAPP3_1_OR_GREATER && !NET5_0_OR_GREATER
+#if NETFRAMEWORK 
 
 namespace System.Diagnostics.CodeAnalysis
 {
-#if !NETSTANDARD2_1
     /// <summary>Specifies that null is allowed as an input even if the corresponding type disallows it.</summary>
     [AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property, Inherited = false)]
 #if SYSTEM_PRIVATE_CORELIB
@@ -135,7 +134,6 @@ sealed class DoesNotReturnIfAttribute : Attribute
         /// <summary>Gets the condition parameter value.</summary>
         public bool ParameterValue { get; }
     }
-#endif
 
     /// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values.</summary>
     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
diff --git a/src/NuGet.Core/Microsoft.Build.NuGetSdkResolver/FileSystemInfoFullNameEqualityComparer.cs b/src/NuGet.Core/Microsoft.Build.NuGetSdkResolver/FileSystemInfoFullNameEqualityComparer.cs
index a1837ab01ab..22f5908d2aa 100644
--- a/src/NuGet.Core/Microsoft.Build.NuGetSdkResolver/FileSystemInfoFullNameEqualityComparer.cs
+++ b/src/NuGet.Core/Microsoft.Build.NuGetSdkResolver/FileSystemInfoFullNameEqualityComparer.cs
@@ -44,7 +44,7 @@ public bool Equals(FileSystemInfo x, FileSystemInfo y)
         /// <returns>A hash code for the specified <see cref="FileSystemInfo" /> object's <see cref="FileSystemInfo.FullName" /> property..</returns>
         public int GetHashCode(FileSystemInfo obj)
         {
-#if NETFRAMEWORK || NETSTANDARD
+#if NETFRAMEWORK
             return obj.FullName.GetHashCode();
 #else
             return obj.FullName.GetHashCode(StringComparison.Ordinal);
diff --git a/src/NuGet.Core/NuGet.Build.Tasks/GetReferenceNearestTargetFrameworkTask.cs b/src/NuGet.Core/NuGet.Build.Tasks/GetReferenceNearestTargetFrameworkTask.cs
index d577b03a212..f74fc685e57 100644
--- a/src/NuGet.Core/NuGet.Build.Tasks/GetReferenceNearestTargetFrameworkTask.cs
+++ b/src/NuGet.Core/NuGet.Build.Tasks/GetReferenceNearestTargetFrameworkTask.cs
@@ -213,7 +213,7 @@ private static bool TryParseFramework(string framework, string errorMessage, MSB
         private static bool TryParseFramework(string targetFrameworkMoniker, string targetPlatformMoniker, string errorMessage, MSBuildLogger logger, out NuGetFramework nugetFramework)
         {
             // Check if we have a long name.
-#if NETFRAMEWORK || NETSTANDARD
+#if NETFRAMEWORK
             nugetFramework = targetFrameworkMoniker.Contains(',')
                 ? NuGetFramework.ParseComponents(targetFrameworkMoniker, targetPlatformMoniker)
                 : NuGetFramework.Parse(targetFrameworkMoniker);
diff --git a/src/NuGet.Core/NuGet.Commands/Internal/HashCodeCombiner.cs b/src/NuGet.Core/NuGet.Commands/Internal/HashCodeCombiner.cs
index 15badf1abb7..0913a43d755 100644
--- a/src/NuGet.Core/NuGet.Commands/Internal/HashCodeCombiner.cs
+++ b/src/NuGet.Core/NuGet.Commands/Internal/HashCodeCombiner.cs
@@ -5,7 +5,7 @@
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 
-#if !NETFRAMEWORK && !NETSTANDARD
+#if NET
 using System;
 #endif
 
@@ -61,7 +61,7 @@ public void Add(int i)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public void Add(string s)
         {
-#if NETFRAMEWORK || NETSTANDARD
+#if NETFRAMEWORK
             var hashCode = (s != null) ? s.GetHashCode() : 0;
 #else
             var hashCode = (s != null) ? s.GetHashCode(StringComparison.Ordinal) : 0;
diff --git a/src/NuGet.Core/NuGet.DependencyResolver.Core/GraphModel/Tracker.cs b/src/NuGet.Core/NuGet.DependencyResolver.Core/GraphModel/Tracker.cs
index 613b4908626..239c433e4fc 100644
--- a/src/NuGet.Core/NuGet.DependencyResolver.Core/GraphModel/Tracker.cs
+++ b/src/NuGet.Core/NuGet.DependencyResolver.Core/GraphModel/Tracker.cs
@@ -115,11 +115,7 @@ public void AddItem(GraphItem<TItem> item)
                 {
                     if (!existingItem.Equals(item))
                     {
-#if NETSTANDARD2_0
-                        _storage = new HashSet<GraphItem<TItem>>() { existingItem, item };
-#else
                         _storage = new HashSet<GraphItem<TItem>>(capacity: 3) { existingItem, item };
-#endif
                     }
                 }
                 else
diff --git a/src/NuGet.Core/NuGet.Packaging/ContentModel/ContentItemCollection.cs b/src/NuGet.Core/NuGet.Packaging/ContentModel/ContentItemCollection.cs
index 8b18ec3e768..59c51d8a7ff 100644
--- a/src/NuGet.Core/NuGet.Packaging/ContentModel/ContentItemCollection.cs
+++ b/src/NuGet.Core/NuGet.Packaging/ContentModel/ContentItemCollection.cs
@@ -378,7 +378,7 @@ public int GetHashCode(ContentItem obj)
                 {
                     foreach (var property in obj._properties)
                     {
-#if NETFRAMEWORK || NETSTANDARD
+#if NETFRAMEWORK
                         hashCode ^= property.Key.GetHashCode();
 #else
                         hashCode ^= property.Key.GetHashCode(StringComparison.Ordinal);
diff --git a/src/NuGet.Core/NuGet.Packaging/PackageCreation/Authoring/PhysicalPackageFile.cs b/src/NuGet.Core/NuGet.Packaging/PackageCreation/Authoring/PhysicalPackageFile.cs
index 41a8b9ed62e..ad0c90b3071 100644
--- a/src/NuGet.Core/NuGet.Packaging/PackageCreation/Authoring/PhysicalPackageFile.cs
+++ b/src/NuGet.Core/NuGet.Packaging/PackageCreation/Authoring/PhysicalPackageFile.cs
@@ -117,7 +117,7 @@ public override int GetHashCode()
             int hash = 0;
             if (SourcePath != null)
             {
-#if NETFRAMEWORK || NETSTANDARD
+#if NETFRAMEWORK
                 hash = SourcePath.GetHashCode();
 #else
                 hash = SourcePath.GetHashCode(StringComparison.Ordinal);
@@ -126,7 +126,7 @@ public override int GetHashCode()
 
             if (TargetPath != null)
             {
-#if NETFRAMEWORK || NETSTANDARD
+#if NETFRAMEWORK
                 hash = hash * 4567 + TargetPath.GetHashCode();
 #else
                 hash = hash * 4567 + TargetPath.GetHashCode(StringComparison.Ordinal);
diff --git a/src/NuGet.Core/NuGet.Packaging/PackageExtraction/StreamExtensions.cs b/src/NuGet.Core/NuGet.Packaging/PackageExtraction/StreamExtensions.cs
index 574953fdb04..2ff3164db68 100644
--- a/src/NuGet.Core/NuGet.Packaging/PackageExtraction/StreamExtensions.cs
+++ b/src/NuGet.Core/NuGet.Packaging/PackageExtraction/StreamExtensions.cs
@@ -6,10 +6,6 @@
 using System.IO.MemoryMappedFiles;
 using NuGet.Common;
 
-#if NETFRAMEWORK || NETSTANDARD2_0
-using System.Buffers;
-#endif
-
 namespace NuGet.Packaging
 {
     public static class StreamExtensions
@@ -19,28 +15,6 @@ public static string CopyToFile(this Stream inputStream, string fileFullPath)
             return Testable.Default.CopyToFile(inputStream, fileFullPath);
         }
 
-        private static void CopyTo(Stream inputStream, Stream outputStream)
-        {
-            // .NET Framework allocates an unavoidable byte[] when using
-            // Stream.CopyTo. Reimplement it, pulling from the pool similar
-            // to .NET 5.
-
-#if NETFRAMEWORK || NETSTANDARD2_0
-            const int bufferSize = 81920; // Same as Stream.CopyTo
-            byte[] buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
-
-            int bytesRead;
-            while ((bytesRead = inputStream.Read(buffer, offset: 0, buffer.Length)) != 0)
-            {
-                outputStream.Write(buffer, offset: 0, bytesRead);
-            }
-
-            ArrayPool<byte>.Shared.Return(buffer);
-#else
-            inputStream.CopyTo(outputStream);
-#endif
-        }
-
         internal class Testable
         {
             // Only files smaller than this value will be mmap'ed
@@ -127,7 +101,7 @@ internal virtual void MmapCopy(Stream inputStream, string fileFullPath, long siz
                     using (MemoryMappedFile mmf = MemoryMappedFile.CreateFromFile(fileFullPath, FileMode.Open, mapName: null, size))
                     using (MemoryMappedViewStream mmstream = mmf.CreateViewStream())
                     {
-                        CopyTo(inputStream, mmstream);
+                        inputStream.CopyTo(mmstream);
                     }
                 }
             }
@@ -136,7 +110,7 @@ internal virtual void FileStreamCopy(Stream inputStream, string fileFullPath)
             {
                 using (var outputStream = NuGetExtractionFileIO.CreateFile(fileFullPath))
                 {
-                    CopyTo(inputStream, outputStream);
+                    inputStream.CopyTo(outputStream);
                 }
             }
         }
diff --git a/src/NuGet.Core/NuGet.Packaging/RuntimeModel/RuntimeGraph.cs b/src/NuGet.Core/NuGet.Packaging/RuntimeModel/RuntimeGraph.cs
index 36715ca4901..9938388c12f 100644
--- a/src/NuGet.Core/NuGet.Packaging/RuntimeModel/RuntimeGraph.cs
+++ b/src/NuGet.Core/NuGet.Packaging/RuntimeModel/RuntimeGraph.cs
@@ -267,13 +267,7 @@ public IEnumerable<RuntimePackageDependency> FindRuntimeDependencies(string runt
             if (_packagesWithDependencies.Contains(packageId))
             {
                 var key = new RuntimeDependencyKey(runtimeName, packageId);
-
-#if NET472_OR_GREATER || NET5_0_OR_GREATER
-
                 return _dependencyCache!.GetOrAdd(key, FindRuntimeDependenciesInternal, this);
-#else
-                return _dependencyCache!.GetOrAdd(key, key => FindRuntimeDependenciesInternal(key, this));
-#endif
             }
 
             return Enumerable.Empty<RuntimePackageDependency>();
diff --git a/src/NuGet.Core/NuGet.ProjectModel/NoAllocNewLineStreamWriter.cs b/src/NuGet.Core/NuGet.ProjectModel/NoAllocNewLineStreamWriter.cs
index 0c90ee7fc91..d8a4c1d65d8 100644
--- a/src/NuGet.Core/NuGet.ProjectModel/NoAllocNewLineStreamWriter.cs
+++ b/src/NuGet.Core/NuGet.ProjectModel/NoAllocNewLineStreamWriter.cs
@@ -1,7 +1,7 @@
 // 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.
 
-#if NETFRAMEWORK || NETSTANDARD2_0_OR_GREATER
+#if NETFRAMEWORK
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
diff --git a/src/NuGet.Core/NuGet.ProjectModel/ProjectRestoreMetadata.cs b/src/NuGet.Core/NuGet.ProjectModel/ProjectRestoreMetadata.cs
index f7d282b9a6f..afb611f31a4 100644
--- a/src/NuGet.Core/NuGet.ProjectModel/ProjectRestoreMetadata.cs
+++ b/src/NuGet.Core/NuGet.ProjectModel/ProjectRestoreMetadata.cs
@@ -243,11 +243,7 @@ public bool Equals(ProjectRestoreMetadata other)
 
         private HashSet<string> GetSources(IList<PackageSource> sources)
         {
-#if NETSTANDARD2_0
-            var setSources = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
-#else
             var setSources = new HashSet<string>(sources.Count, StringComparer.OrdinalIgnoreCase);
-#endif
             for (var i = 0; i < sources.Count; i++)
             {
                 setSources.Add(sources[i].Source);
diff --git a/src/NuGet.Core/NuGet.Protocol/HttpSource/HttpHandlerResourceV3Provider.cs b/src/NuGet.Core/NuGet.Protocol/HttpSource/HttpHandlerResourceV3Provider.cs
index f6b2102e7d9..15cde60c353 100644
--- a/src/NuGet.Core/NuGet.Protocol/HttpSource/HttpHandlerResourceV3Provider.cs
+++ b/src/NuGet.Core/NuGet.Protocol/HttpSource/HttpHandlerResourceV3Provider.cs
@@ -11,22 +11,12 @@
 using NuGet.Configuration;
 using NuGet.Protocol.Core.Types;
 
-#if NETSTANDARD2_0
-using System.Net.Security;
-using System.Security.Cryptography.X509Certificates;
-#endif
-
 namespace NuGet.Protocol
 {
     public class HttpHandlerResourceV3Provider : ResourceProvider
     {
         private readonly IProxyCache _proxyCache;
 
-#if NETSTANDARD2_0
-        internal static Func<HttpRequestMessage, X509Certificate2, X509Chain, SslPolicyErrors, bool> DangerousAcceptAnyServerCertificateValidator =
-            (message, certificate, chain, policyErrors) => true;
-#endif
-
         public HttpHandlerResourceV3Provider()
             : this(ProxyCache.Instance)
         {
@@ -66,17 +56,10 @@ private HttpHandlerResourceV3 CreateResource(PackageSource packageSource)
                 AutomaticDecompression = (DecompressionMethods.GZip | DecompressionMethods.Deflate),
             };
 
-#if NETSTANDARD2_0
-            if (packageSource.DisableTLSCertificateValidation)
-            {
-                clientHandler.ServerCertificateCustomValidationCallback = DangerousAcceptAnyServerCertificateValidator;
-            }
-#else
             if (packageSource.DisableTLSCertificateValidation)
             {
                 clientHandler.ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator;
             }
-#endif
 
 #if IS_DESKTOP
             if (packageSource.MaxHttpRequestsPerSource > 0)
diff --git a/src/NuGet.Core/NuGet.Protocol/RemoteRepositories/HttpFileSystemBasedFindPackageByIdResource.cs b/src/NuGet.Core/NuGet.Protocol/RemoteRepositories/HttpFileSystemBasedFindPackageByIdResource.cs
index aa681cdc5c8..f35c1b0a50e 100644
--- a/src/NuGet.Core/NuGet.Protocol/RemoteRepositories/HttpFileSystemBasedFindPackageByIdResource.cs
+++ b/src/NuGet.Core/NuGet.Protocol/RemoteRepositories/HttpFileSystemBasedFindPackageByIdResource.cs
@@ -432,23 +432,12 @@ private static bool TryGetVersionString(NuGetVersion version, HashSet<NuGetVersi
                 return false;
             }
 
-#if !NETSTANDARD
             if (!packageVersions.TryGetValue(version, out NuGetVersion? originalVersion))
             {
                 versionString = null;
                 return false;
             }
             versionString = originalVersion.ToNormalizedString();
-#else
-            // .NET Standard 2.0 doesn't support HashSet<T>.TryGetValue. The API docs say the version should be lowercase, but if
-            // a server doesn't follow the spec and uses case sensitive URLs, this might result in 404 responses.
-            if (!packageVersions.Contains(version))
-            {
-                versionString = null;
-                return false;
-            }
-            versionString = version.ToNormalizedString().ToLowerInvariant();
-#endif
 
             return true;
         }
@@ -582,12 +571,7 @@ private static async Task<HashSet<NuGetVersion>> ConsumeFlatContainerIndexAsync(
         {
             var json = await JsonSerializer.DeserializeAsync(stream, JsonContext.Default.FlatContainerVersionList, cancellationToken: token);
 
-            var result =
-#if NETSTANDARD
-                new HashSet<NuGetVersion>();
-#else
-                new HashSet<NuGetVersion>(capacity: json.Versions?.Count ?? 0);
-#endif
+            var result = new HashSet<NuGetVersion>(capacity: json.Versions?.Count ?? 0);
 
             foreach (var versionString in json.Versions ?? [])
             {
diff --git a/src/NuGet.Core/NuGet.Protocol/Resources/VulnerabilityInfoResourceV3.cs b/src/NuGet.Core/NuGet.Protocol/Resources/VulnerabilityInfoResourceV3.cs
index 4bbbdfd0c84..9112963ca77 100644
--- a/src/NuGet.Core/NuGet.Protocol/Resources/VulnerabilityInfoResourceV3.cs
+++ b/src/NuGet.Core/NuGet.Protocol/Resources/VulnerabilityInfoResourceV3.cs
@@ -197,12 +197,7 @@ public async Task<GetVulnerabilityInfoResult> GetVulnerabilityInfoAsync(SourceCa
         private IReadOnlyList<V3VulnerabilityIndexEntry> GetValidIndexEntries(IReadOnlyList<V3VulnerabilityIndexEntry> indexEntries, ref List<Exception>? exceptions)
         {
             List<V3VulnerabilityIndexEntry> validIndexEntries = new(indexEntries.Count);
-            HashSet<string> pageNames =
-#if NETSTANDARD
-                new(comparer: StringComparer.InvariantCultureIgnoreCase);
-#else
-                new(indexEntries.Count, StringComparer.InvariantCultureIgnoreCase);
-#endif
+            HashSet<string> pageNames = new(indexEntries.Count, StringComparer.InvariantCultureIgnoreCase);
 
             for (int i = 0; i < indexEntries.Count; i++)
             {