Mark DirectoryServices CAS APIs as Obsolete

src/libraries/Directory.Build.targets

@@ -253,6 +253,19 @@
     </When>
   </Choose>
 
+  <!-- Adds ObsoleteAttribute to projects that need to apply downlevel Obsoletions with DiagnosticId and UrlFormat -->
+  <Choose>
+    <When Condition="'$(IncludeInternalObsoleteAttribute)' == 'true' and ($(TargetFramework.StartsWith('netstandard')) or $(TargetFramework.StartsWith('netcoreapp')) or '$(TargetFrameworkIdentifier)' == '.NETFramework')">
+      <ItemGroup>
+        <Compile Include="$(CoreLibSharedDir)System\ObsoleteAttribute.cs" Link="System\ObsoleteAttribute.cs" />
+      </ItemGroup>
+      <PropertyGroup>
+        <!-- Suppress CS0436 to allow ObsoleteAttribute to be internally defined and used in netstandard -->
+        <NoWarn>$(NoWarn);CS0436</NoWarn>
+      </PropertyGroup>
+    </When>
+  </Choose>
+
   <!-- The Default behavior in VS is to show files for the first target framework in TargetFrameworks property.
         This is required to show all the files corresponding to all target frameworks in VS. -->
   <ItemGroup>

src/libraries/System.DirectoryServices/ref/System.DirectoryServices.cs

@@ -259,6 +259,7 @@ public DirectoryServicesCOMException(string message, System.Exception inner) { }
         public string ExtendedErrorMessage { get { throw null; } }
         public override void GetObjectData(System.Runtime.Serialization.SerializationInfo serializationInfo, System.Runtime.Serialization.StreamingContext streamingContext) { }
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     public sealed partial class DirectoryServicesPermission : System.Security.Permissions.ResourcePermissionBase
     {
         public DirectoryServicesPermission() { }
@@ -274,6 +275,7 @@ public enum DirectoryServicesPermissionAccess
         Browse = 2,
         Write = 6,
     }
+    [System.ObsoleteAttribute("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
     [System.AttributeUsageAttribute(System.AttributeTargets.Assembly | System.AttributeTargets.Class | System.AttributeTargets.Constructor | System.AttributeTargets.Event | System.AttributeTargets.Method | System.AttributeTargets.Struct, AllowMultiple=true, Inherited=false)]
     public partial class DirectoryServicesPermissionAttribute : System.Security.Permissions.CodeAccessSecurityAttribute
     {

src/libraries/System.DirectoryServices/ref/System.DirectoryServices.csproj

@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
+    <IncludeInternalObsoleteAttribute>true</IncludeInternalObsoleteAttribute>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System.DirectoryServices.cs" />

src/libraries/System.DirectoryServices/src/System.DirectoryServices.csproj

@@ -3,6 +3,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <TargetFrameworks>$(NetCoreAppCurrent)-Windows_NT;netstandard2.0;netcoreapp2.0-Windows_NT</TargetFrameworks>
     <ExcludeCurrentNetCoreAppFromPackage>true</ExcludeCurrentNetCoreAppFromPackage>
+    <IncludeInternalObsoleteAttribute>true</IncludeInternalObsoleteAttribute>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -135,6 +136,7 @@
     <Compile Include="Interop\NativeMethods.cs" />
     <Compile Include="Interop\SafeNativeMethods.cs" />
     <Compile Include="Interop\UnsafeNativeMethods.cs" />
+    <Compile Include="$(CommonPath)System\Obsoletions.cs" Link="System\Obsoletions.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)System.Security.Permissions\src\System.Security.Permissions.csproj" />

src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermission.cs

@@ -5,9 +5,7 @@
 
 namespace System.DirectoryServices
 {
-#pragma warning disable SYSLIB0003
-    // Conditionally marking this type as obsolete in .NET 5+ will require diverging its net5.0 build from netstandard2.0
-    // https://github.com/dotnet/runtime/issues/39413
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     public sealed class DirectoryServicesPermission : ResourcePermissionBase
     {
         public DirectoryServicesPermission() { }
@@ -16,5 +14,4 @@ public DirectoryServicesPermission(PermissionState state) { }
         public DirectoryServicesPermission(DirectoryServicesPermissionAccess permissionAccess, string path) { }
         public DirectoryServicesPermissionEntryCollection PermissionEntries { get; }
     }
-#pragma warning restore SYSLIB0003
 }

src/libraries/System.DirectoryServices/src/System/DirectoryServices/DirectoryServicesPermissionAttribute.cs

@@ -6,9 +6,7 @@
 
 namespace System.DirectoryServices
 {
-#pragma warning disable SYSLIB0003
-    // Conditionally marking this type as obsolete in .NET 5+ will require diverging its net5.0 build from netstandard2.0
-    // https://github.com/dotnet/runtime/issues/39413
+    [Obsolete(Obsoletions.CodeAccessSecurityMessage, DiagnosticId = Obsoletions.CodeAccessSecurityDiagId, UrlFormat = Obsoletions.SharedUrlFormat)]
     [AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class | AttributeTargets.Struct |
         AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Event,
         AllowMultiple = true, Inherited = false)]
@@ -19,5 +17,4 @@ public DirectoryServicesPermissionAttribute(SecurityAction action) : base(defaul
         public string Path { get; set; }
         public override IPermission CreatePermission() { return default(IPermission); }
     }
-#pragma warning restore SYSLIB0003
 }

src/libraries/System.Private.CoreLib/src/System/ObsoleteAttribute.cs

@@ -24,7 +24,13 @@ namespace System
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Enum |
         AttributeTargets.Interface | AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Event | AttributeTargets.Delegate,
         Inherited = false)]
-    public sealed class ObsoleteAttribute : Attribute
+#if SYSTEM_PRIVATE_CORELIB
+    public
+#else
+#nullable enable
+    internal
+#endif
+    sealed class ObsoleteAttribute : Attribute
     {
         public ObsoleteAttribute()
         {