diff --git a/Directory.Build.props b/Directory.Build.props
index 32d532c8..d3047adb 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -67,10 +67,39 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.CodeAnalysis.FxCopAnalyzers" PrivateAssets="All" />
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Condition=" '$(OS)' != 'Windows_NT' " PrivateAssets="All" />
   </ItemGroup>
 
+  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' ">
+    <DefineConstants>$(DefineConstants);SUPPORTS_ECDSA</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' And '$(TargetFramework)' != 'netstandard2.0' ">
+    <DefineConstants>$(DefineConstants);SUPPORTS_CERTIFICATE_GENERATION</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_DIRECT_KEY_CREATION_WITH_SPECIFIED_SIZE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_EPHEMERAL_KEY_SETS</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_KEY_DERIVATION_WITH_SPECIFIED_HASH_ALGORITHM</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' And
+                             '$(TargetFramework)' != 'net472' And
+                             '$(TargetFramework)' != 'netstandard2.0' ">
+    <DefineConstants>$(DefineConstants);SUPPORTS_BASE64_SPAN_CONVERSION</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_STATIC_RANDOM_NUMBER_GENERATOR_METHODS</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_TIME_CONSTANT_COMPARISONS</DefineConstants>
+  </PropertyGroup>
+
+  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' And
+                             '$(TargetFramework)' != 'net472' And
+                             '$(TargetFramework)' != 'netcoreapp2.1' And
+                             '$(TargetFramework)' != 'netstandard2.0' ">
+    <DefineConstants>$(DefineConstants);SUPPORTS_BCL_ASYNC_ENUMERABLE</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_GENERIC_HOST</DefineConstants>
+    <DefineConstants>$(DefineConstants);SUPPORTS_SERVICE_PROVIDER_IN_HTTP_MESSAGE_HANDLER_BUILDER</DefineConstants>
+  </PropertyGroup>
+
   <ItemGroup>
     <ProjectCapability Include="DynamicDependentFile" />
     <ProjectCapability Include="DynamicFileNesting" />
diff --git a/src/OpenIddict.Abstractions/OpenIddict.Abstractions.csproj b/src/OpenIddict.Abstractions/OpenIddict.Abstractions.csproj
index 3888b0f1..0e312257 100644
--- a/src/OpenIddict.Abstractions/OpenIddict.Abstractions.csproj
+++ b/src/OpenIddict.Abstractions/OpenIddict.Abstractions.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -9,16 +9,22 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" />
     <PackageReference Include="Microsoft.Extensions.Primitives" />
     <PackageReference Include="System.Collections.Immutable" />
-    <PackageReference Include="System.ComponentModel.Annotations" />
     <PackageReference Include="System.Text.Json" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETFramework' Or '$(TargetFramework)' == 'netstandard2.0' ">
     <PackageReference Include="Microsoft.Bcl.HashCode" />
   </ItemGroup>
 
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETFramework' ">
+    <Reference Include="System.ComponentModel.DataAnnotations" />
+  </ItemGroup>
+
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETStandard' ">
+    <PackageReference Include="System.ComponentModel.Annotations" />
+  </ItemGroup>
+
 </Project>
diff --git a/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs b/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
index 21e90944..a0f345b0 100644
--- a/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
+++ b/src/OpenIddict.Core/Managers/OpenIddictApplicationManager.cs
@@ -1263,9 +1263,9 @@ namespace OpenIddict.Core
                 // Write the hashing algorithm version.
                 BinaryPrimitives.WriteUInt32BigEndian(payload.Slice(1, 4), algorithm switch
                 {
-                    { Name: nameof(SHA1)   } => 0,
-                    { Name: nameof(SHA256) } => 1,
-                    { Name: nameof(SHA512) } => 2,
+                    var name when name == HashAlgorithmName.SHA1   => 0,
+                    var name when name == HashAlgorithmName.SHA256 => 1,
+                    var name when name == HashAlgorithmName.SHA512 => 2,
 
                     _ => throw new InvalidOperationException("The specified HMAC algorithm is not valid.")
                 });
@@ -1394,9 +1394,10 @@ namespace OpenIddict.Core
 #else
             var generator = new Pkcs5S2ParametersGenerator(algorithm switch
             {
-                { Name: nameof(SHA1)   } => (IDigest) new Sha1Digest(),
-                { Name: nameof(SHA256) } => new Sha256Digest(),
-                { Name: nameof(SHA512) } => new Sha512Digest(),
+                var name when name == HashAlgorithmName.SHA1   => new Sha1Digest(),
+                var name when name == HashAlgorithmName.SHA256 => new Sha256Digest(),
+                var name when name == HashAlgorithmName.SHA512 => new Sha512Digest(),
+
                 _ => throw new InvalidOperationException("The specified hash algorithm is not valid.")
             });
 
diff --git a/src/OpenIddict.Core/OpenIddict.Core.csproj b/src/OpenIddict.Core/OpenIddict.Core.csproj
index 0738b0aa..f412e23d 100644
--- a/src/OpenIddict.Core/OpenIddict.Core.csproj
+++ b/src/OpenIddict.Core/OpenIddict.Core.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net472;netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net461;net472;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -14,25 +14,18 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Extensions.Caching.Memory" />
     <PackageReference Include="Microsoft.Extensions.Logging" />
     <PackageReference Include="Microsoft.Extensions.Options" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net472' Or '$(TargetFramework)' == 'netstandard2.0' ">
-    <PackageReference Include="Portable.BouncyCastle" />
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETFramework' ">
+    <Reference Include="System.ComponentModel.DataAnnotations" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'net472' Or '$(TargetFramework)' == 'netstandard2.1' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_KEY_DERIVATION_WITH_SPECIFIED_HASH_ALGORITHM</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard2.1' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_BASE64_SPAN_CONVERSION</DefineConstants>
-    <DefineConstants>$(DefineConstants);SUPPORTS_STATIC_RANDOM_NUMBER_GENERATOR_METHODS</DefineConstants>
-    <DefineConstants>$(DefineConstants);SUPPORTS_TIME_CONSTANT_COMPARISONS</DefineConstants>
-  </PropertyGroup>
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETFramework' Or '$(TargetFramework)' == 'netstandard2.0' ">
+    <PackageReference Include="Portable.BouncyCastle" />
+  </ItemGroup>
 
   <ItemGroup>
     <Compile Include="..\..\shared\OpenIddict.Extensions\*\*.cs" />
diff --git a/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj b/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj
index ac709f6a..c23bd436 100644
--- a/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj
+++ b/src/OpenIddict.EntityFramework.Models/OpenIddict.EntityFramework.Models.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>net461;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/src/OpenIddict.EntityFramework/OpenIddict.EntityFramework.csproj b/src/OpenIddict.EntityFramework/OpenIddict.EntityFramework.csproj
index a1d190bf..ce7d3b6d 100644
--- a/src/OpenIddict.EntityFramework/OpenIddict.EntityFramework.csproj
+++ b/src/OpenIddict.EntityFramework/OpenIddict.EntityFramework.csproj
@@ -16,7 +16,6 @@
 
   <ItemGroup>
     <PackageReference Include="EntityFramework" />
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj
index 48d36bcf..34675b6b 100644
--- a/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj
+++ b/src/OpenIddict.EntityFrameworkCore.Models/OpenIddict.EntityFrameworkCore.Models.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>net461;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
diff --git a/src/OpenIddict.EntityFrameworkCore/OpenIddict.EntityFrameworkCore.csproj b/src/OpenIddict.EntityFrameworkCore/OpenIddict.EntityFrameworkCore.csproj
index efe311f3..32e7cd2a 100644
--- a/src/OpenIddict.EntityFrameworkCore/OpenIddict.EntityFrameworkCore.csproj
+++ b/src/OpenIddict.EntityFrameworkCore/OpenIddict.EntityFrameworkCore.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -15,7 +15,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Relational" />
   </ItemGroup>
 
@@ -23,8 +22,4 @@
     <Compile Include="..\..\shared\OpenIddict.Extensions\*\*.cs" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'netstandard2.1' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_BCL_ASYNC_ENUMERABLE</DefineConstants>
-  </PropertyGroup>
-
 </Project>
diff --git a/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj b/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj
index be028480..0b6fd067 100644
--- a/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj
+++ b/src/OpenIddict.MongoDb.Models/OpenIddict.MongoDb.Models.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>netstandard2.0</TargetFramework>
+    <TargetFrameworks>net461;netstandard2.0</TargetFrameworks>
     <SignAssembly>false</SignAssembly>
     <PublicSign>false</PublicSign>
   </PropertyGroup>
diff --git a/src/OpenIddict.MongoDb/OpenIddict.MongoDb.csproj b/src/OpenIddict.MongoDb/OpenIddict.MongoDb.csproj
index 32b1bff8..212319a1 100644
--- a/src/OpenIddict.MongoDb/OpenIddict.MongoDb.csproj
+++ b/src/OpenIddict.MongoDb/OpenIddict.MongoDb.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;netstandard2.1</TargetFrameworks>
     <SignAssembly>false</SignAssembly>
     <PublicSign>false</PublicSign>
   </PropertyGroup>
@@ -17,7 +17,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="MongoDB.Driver" />
   </ItemGroup>
 
diff --git a/src/OpenIddict.Server.AspNetCore/OpenIddict.Server.AspNetCore.csproj b/src/OpenIddict.Server.AspNetCore/OpenIddict.Server.AspNetCore.csproj
index 1bdc97a0..eca31f7f 100644
--- a/src/OpenIddict.Server.AspNetCore/OpenIddict.Server.AspNetCore.csproj
+++ b/src/OpenIddict.Server.AspNetCore/OpenIddict.Server.AspNetCore.csproj
@@ -13,22 +13,16 @@
     <ProjectReference Include="..\OpenIddict.Server\OpenIddict.Server.csproj" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETCoreApp' And
+                          $([MSBuild]::VersionGreaterThanOrEquals($(TargetFrameworkVersion), '3.1')) ">
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' != 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' != '.NETCoreApp' Or
+                          $([MSBuild]::VersionLessThan($(TargetFrameworkVersion), '3.1')) ">
     <PackageReference Include="Microsoft.AspNetCore.Authentication" />
     <PackageReference Include="Microsoft.AspNetCore.Diagnostics.Abstractions" />
     <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
-  </ItemGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_STATIC_RANDOM_NUMBER_GENERATOR_METHODS</DefineConstants>
-  </PropertyGroup>
-
 </Project>
diff --git a/src/OpenIddict.Server.DataProtection/OpenIddict.Server.DataProtection.csproj b/src/OpenIddict.Server.DataProtection/OpenIddict.Server.DataProtection.csproj
index 696d20aa..78d4be56 100644
--- a/src/OpenIddict.Server.DataProtection/OpenIddict.Server.DataProtection.csproj
+++ b/src/OpenIddict.Server.DataProtection/OpenIddict.Server.DataProtection.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net461;netcoreapp3.1;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -13,15 +13,13 @@
     <ProjectReference Include="..\OpenIddict.Server\OpenIddict.Server.csproj" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETCoreApp' And
+                          $([MSBuild]::VersionGreaterThanOrEquals($(TargetFrameworkVersion), '3.1')) ">
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' != 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' != '.NETCoreApp' Or
+                          $([MSBuild]::VersionLessThan($(TargetFrameworkVersion), '3.1')) ">
     <PackageReference Include="Microsoft.AspNetCore.DataProtection" />
   </ItemGroup>
 
diff --git a/src/OpenIddict.Server.Owin/OpenIddict.Server.Owin.csproj b/src/OpenIddict.Server.Owin/OpenIddict.Server.Owin.csproj
index f9a62e15..0892e17a 100644
--- a/src/OpenIddict.Server.Owin/OpenIddict.Server.Owin.csproj
+++ b/src/OpenIddict.Server.Owin/OpenIddict.Server.Owin.csproj
@@ -14,7 +14,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" />
     <PackageReference Include="Microsoft.Extensions.WebEncoders" />
     <PackageReference Include="Microsoft.Owin.Security" />
diff --git a/src/OpenIddict.Server/OpenIddict.Server.csproj b/src/OpenIddict.Server/OpenIddict.Server.csproj
index 7e094ab0..ad8f04ec 100644
--- a/src/OpenIddict.Server/OpenIddict.Server.csproj
+++ b/src/OpenIddict.Server/OpenIddict.Server.csproj
@@ -17,7 +17,6 @@ To use the server feature on ASP.NET Core or OWIN/Katana, reference the OpenIddi
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Extensions.Logging" />
     <PackageReference Include="Microsoft.IdentityModel.JsonWebTokens" />
   </ItemGroup>
@@ -28,22 +27,4 @@ To use the server feature on ASP.NET Core or OWIN/Katana, reference the OpenIddi
     <PackageReference Include="Portable.BouncyCastle" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_ECDSA</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' And '$(TargetFramework)' != 'netstandard2.0' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_CERTIFICATE_GENERATION</DefineConstants>
-    <DefineConstants>$(DefineConstants);SUPPORTS_DIRECT_KEY_CREATION_WITH_SPECIFIED_SIZE</DefineConstants>
-    <DefineConstants>$(DefineConstants);SUPPORTS_EPHEMERAL_KEY_SETS</DefineConstants>
-  </PropertyGroup>
-
-  <PropertyGroup Condition=" '$(TargetFramework)' == 'netcoreapp2.1' Or
-                             '$(TargetFramework)' == 'netcoreapp3.1' Or
-                             '$(TargetFramework)' == 'netstandard2.1' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_CERTIFICATE_HASHING_WITH_SPECIFIED_ALGORITHM</DefineConstants>
-    <DefineConstants>$(DefineConstants);SUPPORTS_STATIC_RANDOM_NUMBER_GENERATOR_METHODS</DefineConstants>
-    <DefineConstants>$(DefineConstants);SUPPORTS_TIME_CONSTANT_COMPARISONS</DefineConstants>
-  </PropertyGroup>
-
 </Project>
diff --git a/src/OpenIddict.Validation.AspNetCore/OpenIddict.Validation.AspNetCore.csproj b/src/OpenIddict.Validation.AspNetCore/OpenIddict.Validation.AspNetCore.csproj
index 902e6809..6190f86e 100644
--- a/src/OpenIddict.Validation.AspNetCore/OpenIddict.Validation.AspNetCore.csproj
+++ b/src/OpenIddict.Validation.AspNetCore/OpenIddict.Validation.AspNetCore.csproj
@@ -13,16 +13,14 @@
     <ProjectReference Include="..\OpenIddict.Validation\OpenIddict.Validation.csproj" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETCoreApp' And
+                          $([MSBuild]::VersionGreaterThanOrEquals($(TargetFrameworkVersion), '3.1')) ">
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' != 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' != '.NETCoreApp' Or
+                          $([MSBuild]::VersionLessThan($(TargetFrameworkVersion), '3.1')) ">
     <PackageReference Include="Microsoft.AspNetCore.Authentication" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
-  </ItemGroup>
-
 </Project>
diff --git a/src/OpenIddict.Validation.DataProtection/OpenIddict.Validation.DataProtection.csproj b/src/OpenIddict.Validation.DataProtection/OpenIddict.Validation.DataProtection.csproj
index 8efdd72b..4435b8e0 100644
--- a/src/OpenIddict.Validation.DataProtection/OpenIddict.Validation.DataProtection.csproj
+++ b/src/OpenIddict.Validation.DataProtection/OpenIddict.Validation.DataProtection.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1;netcoreapp3.1</TargetFrameworks>
+    <TargetFrameworks>net461;netcoreapp3.1;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -13,15 +13,13 @@
     <ProjectReference Include="..\OpenIddict.Validation\OpenIddict.Validation.csproj" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETCoreApp' And
+                          $([MSBuild]::VersionGreaterThanOrEquals($(TargetFrameworkVersion), '3.1')) ">
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
-  </ItemGroup>
-
-  <ItemGroup Condition=" '$(TargetFramework)' != 'netcoreapp3.1' ">
+  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' != '.NETCoreApp' Or
+                          $([MSBuild]::VersionLessThan($(TargetFrameworkVersion), '3.1')) ">
     <PackageReference Include="Microsoft.AspNetCore.DataProtection" />
   </ItemGroup>
 
diff --git a/src/OpenIddict.Validation.Owin/OpenIddict.Validation.Owin.csproj b/src/OpenIddict.Validation.Owin/OpenIddict.Validation.Owin.csproj
index 215bde69..8d50be74 100644
--- a/src/OpenIddict.Validation.Owin/OpenIddict.Validation.Owin.csproj
+++ b/src/OpenIddict.Validation.Owin/OpenIddict.Validation.Owin.csproj
@@ -14,7 +14,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" />
     <PackageReference Include="Microsoft.Owin.Security" />
   </ItemGroup>
diff --git a/src/OpenIddict.Validation.ServerIntegration/OpenIddict.Validation.ServerIntegration.csproj b/src/OpenIddict.Validation.ServerIntegration/OpenIddict.Validation.ServerIntegration.csproj
index 3362f2f6..2328cadd 100644
--- a/src/OpenIddict.Validation.ServerIntegration/OpenIddict.Validation.ServerIntegration.csproj
+++ b/src/OpenIddict.Validation.ServerIntegration/OpenIddict.Validation.ServerIntegration.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -14,8 +14,4 @@
     <ProjectReference Include="..\OpenIddict.Validation\OpenIddict.Validation.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
-  </ItemGroup>
-
 </Project>
diff --git a/src/OpenIddict.Validation.SystemNetHttp/OpenIddict.Validation.SystemNetHttp.csproj b/src/OpenIddict.Validation.SystemNetHttp/OpenIddict.Validation.SystemNetHttp.csproj
index f6d13caf..90dfd21f 100644
--- a/src/OpenIddict.Validation.SystemNetHttp/OpenIddict.Validation.SystemNetHttp.csproj
+++ b/src/OpenIddict.Validation.SystemNetHttp/OpenIddict.Validation.SystemNetHttp.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;netstandard2.1</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -15,12 +15,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Http.Polly" />
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="System.Net.Http.Json" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' != 'netstandard2.0' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_SERVICE_PROVIDER_IN_HTTP_MESSAGE_HANDLER_BUILDER</DefineConstants>
-  </PropertyGroup>
-
 </Project>
diff --git a/src/OpenIddict.Validation/OpenIddict.Validation.csproj b/src/OpenIddict.Validation/OpenIddict.Validation.csproj
index 44dea8d8..1ba4dc2c 100644
--- a/src/OpenIddict.Validation/OpenIddict.Validation.csproj
+++ b/src/OpenIddict.Validation/OpenIddict.Validation.csproj
@@ -17,13 +17,8 @@ To use the validation feature on ASP.NET Core or OWIN/Katana, reference the Open
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="JetBrains.Annotations" PrivateAssets="All" />
     <PackageReference Include="Microsoft.Extensions.Logging" />
     <PackageReference Include="Microsoft.IdentityModel.Protocols.OpenIdConnect" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' And '$(TargetFramework)' != 'netstandard2.0' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_EPHEMERAL_KEY_SETS</DefineConstants>
-  </PropertyGroup>
-
 </Project>
diff --git a/src/OpenIddict/OpenIddict.csproj b/src/OpenIddict/OpenIddict.csproj
index 7bf94465..206513bd 100644
--- a/src/OpenIddict/OpenIddict.csproj
+++ b/src/OpenIddict/OpenIddict.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net461;netstandard2.0;netstandard2.1</TargetFrameworks>
     <IncludeBuildOutput>false</IncludeBuildOutput>
     <IncludeSymbols>false</IncludeSymbols>
   </PropertyGroup>
diff --git a/test/OpenIddict.Server.AspNetCore.IntegrationTests/OpenIddict.Server.AspNetCore.IntegrationTests.csproj b/test/OpenIddict.Server.AspNetCore.IntegrationTests/OpenIddict.Server.AspNetCore.IntegrationTests.csproj
index 6272d63d..d3c3eff0 100644
--- a/test/OpenIddict.Server.AspNetCore.IntegrationTests/OpenIddict.Server.AspNetCore.IntegrationTests.csproj
+++ b/test/OpenIddict.Server.AspNetCore.IntegrationTests/OpenIddict.Server.AspNetCore.IntegrationTests.csproj
@@ -21,9 +21,4 @@
     <Reference Include="System.Net.Http" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' And '$(TargetFramework)' != 'net472' And
-                             '$(TargetFramework)' != 'netcoreapp2.1'">
-    <DefineConstants>$(DefineConstants);SUPPORTS_GENERIC_HOST</DefineConstants>
-  </PropertyGroup>
-
 </Project>
diff --git a/test/OpenIddict.Server.IntegrationTests/OpenIddict.Server.IntegrationTests.csproj b/test/OpenIddict.Server.IntegrationTests/OpenIddict.Server.IntegrationTests.csproj
index 17c2e923..8af7c81b 100644
--- a/test/OpenIddict.Server.IntegrationTests/OpenIddict.Server.IntegrationTests.csproj
+++ b/test/OpenIddict.Server.IntegrationTests/OpenIddict.Server.IntegrationTests.csproj
@@ -25,8 +25,4 @@
     <Reference Include="System.Net.Http" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_ECDSA</DefineConstants>
-  </PropertyGroup>
-
 </Project>
diff --git a/test/OpenIddict.Server.Tests/OpenIddict.Server.Tests.csproj b/test/OpenIddict.Server.Tests/OpenIddict.Server.Tests.csproj
index 448e67c9..f2179c04 100644
--- a/test/OpenIddict.Server.Tests/OpenIddict.Server.Tests.csproj
+++ b/test/OpenIddict.Server.Tests/OpenIddict.Server.Tests.csproj
@@ -22,9 +22,4 @@
     <Reference Include="System.Net.Http" />
   </ItemGroup>
 
-  <PropertyGroup Condition=" '$(TargetFramework)' != 'net461' ">
-    <DefineConstants>$(DefineConstants);SUPPORTS_ECDSA</DefineConstants>
-    <DefineConstants>$(DefineConstants);SUPPORTS_CERTIFICATE_GENERATION</DefineConstants>
-  </PropertyGroup>
-
 </Project>