stage

src/Elastic.OpenTelemetry/Diagnostics/LoggingEventListener.cs

@@ -16,8 +16,15 @@ internal sealed partial class LoggingEventListener : EventListener, IAsyncDispos
 	private readonly ILogger _logger;
 	private readonly EventLevel _eventLevel = EventLevel.Informational;
 
-	[GeneratedRegex("^\\d{2}-[a-f0-9]{32}-[a-f0-9]{16}-\\d{2}$")]
+	private const string TraceParentRe = "^\\d{2}-[a-f0-9]{32}-[a-f0-9]{16}-\\d{2}$";
+#if NETSTANDARD2_1_OR_GREATER || NET6_0_OR_GREATER
+	[GeneratedRegex(TraceParentRe)]
 	private static partial Regex TraceParentRegex();
+#else
+
+	private static Regex _traceParentRegex = new Regex(TraceParentRe);
+	private static Regex TraceParentRegex() => _traceParentRegex;
+#endif
 
 	public LoggingEventListener(ILogger logger)
 	{

src/Elastic.OpenTelemetry/Elastic.OpenTelemetry.csproj

@@ -2,26 +2,30 @@
 
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFramework>net8.0</TargetFramework>
+    <TargetFrameworks>netstandard2.0;net8.0</TargetFrameworks>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
     <IsPackable>True</IsPackable>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="OpenTelemetry" Version="1.7.0" />
-    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.7.0" />
-
-    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.7.0" />
-    <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.7.0" />
-    <PackageReference Include="OpenTelemetry.Instrumentation.GrpcNetClient" Version="1.6.0-beta.3" />
-    <PackageReference Include="OpenTelemetry.Instrumentation.EntityFrameworkCore" Version="1.0.0-beta.9" />
-    <PackageReference Include="OpenTelemetry.Instrumentation.Runtime" Version="1.7.0" />
-    <PackageReference Include="OpenTelemetry.Instrumentation.Process" Version="0.5.0-beta.4" />
+    <PackageReference Include="OpenTelemetry" Version="1.7.0"/>
+    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.7.0"/>
+
+    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.7.0"/>
+    <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.7.0"/>
+    <PackageReference Include="OpenTelemetry.Instrumentation.GrpcNetClient" Version="1.6.0-beta.3"/>
+    <PackageReference Include="OpenTelemetry.Instrumentation.EntityFrameworkCore" Version="1.0.0-beta.9"/>
+    <PackageReference Include="OpenTelemetry.Instrumentation.Runtime" Version="1.7.0"/>
+    <PackageReference Include="OpenTelemetry.Instrumentation.Process" Version="0.5.0-beta.4"/>
+  </ItemGroup>
+
+  <ItemGroup Condition="'$(TargetFramework)'=='netstandard2.0'">
+    <PackageReference Include="System.Threading.Channels" Version="8.0.0" />
   </ItemGroup>
 
   <ItemGroup>
-    <InternalsVisibleTo Include="Elastic.OpenTelemetry.Tests" Key="$(ExposedPublicKey)" />
+    <InternalsVisibleTo Include="Elastic.OpenTelemetry.Tests" Key="$(ExposedPublicKey)"/>
   </ItemGroup>
-  
+
 </Project>

src/Elastic.OpenTelemetry/Extensions/IsExternalInit.cs

@@ -0,0 +1,23 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+#if NETSTANDARD2_0
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+
+// ReSharper disable once CheckNamespace
+namespace System.Runtime.CompilerServices
+{
+	/// <summary>
+	///     Reserved to be used by the compiler for tracking metadata.
+	///     This class should not be used by developers in source code.
+	/// </summary>
+	/// <remarks>
+	///     This definition is provided by the <i>IsExternalInit</i> NuGet package (https://www.nuget.org/packages/IsExternalInit).
+	///     Please see https://github.com/manuelroemer/IsExternalInit for more information.
+	/// </remarks>
+	[ExcludeFromCodeCoverage, DebuggerNonUserCode]
+	internal static class IsExternalInit;
+}
+#endif