feat: Add basic config for dotnet plugin.

sdk/@launchdarkly/observability-dotnet/.gitignore

@@ -1,2 +1,4 @@
 **/bin
 **/obj
+LaunchDarkly.Observability.sln.DotSettings.user
+**/launchSettings.json

sdk/@launchdarkly/observability-dotnet/AspSampleApp/AspSampleApp.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+    <PropertyGroup>
+        <TargetFramework>net8.0</TargetFramework>
+        <Nullable>enable</Nullable>
+        <ImplicitUsings>enable</ImplicitUsings>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.19"/>
+        <PackageReference Include="Swashbuckle.AspNetCore" Version="6.6.2"/>
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\src\LaunchDarkly.Observability\LaunchDarkly.Observability.csproj" />
+    </ItemGroup>
+
+</Project>

sdk/@launchdarkly/observability-dotnet/AspSampleApp/AspSampleApp.http

@@ -0,0 +1,6 @@
+@AspSampleApp_HostAddress = http://localhost:5247
+
+GET {{AspSampleApp_HostAddress}}/weatherforecast/
+Accept: application/json
+
+###

sdk/@launchdarkly/observability-dotnet/AspSampleApp/Program.cs

@@ -0,0 +1,54 @@
+using LaunchDarkly.Observability;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Add services to the container.
+// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
+builder.Services.AddEndpointsApiExplorer();
+builder.Services.AddSwaggerGen();
+builder.Services.AddLaunchDarklyObservability(
+    Environment.GetEnvironmentVariable("LAUNCHDARKLY_SDK_KEY"),
+    ldBuilder =>
+    {
+        ldBuilder.WithServiceName("ryan-test-service");
+    }
+);
+
+
+var app = builder.Build();
+
+// Configure the HTTP request pipeline.
+if (app.Environment.IsDevelopment())
+{
+    app.UseSwagger();
+    app.UseSwaggerUI();
+}
+
+app.UseHttpsRedirection();
+
+var summaries = new[]
+{
+    "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
+};
+
+app.MapGet("/weatherforecast", () =>
+    {
+        var forecast = Enumerable.Range(1, 5).Select(index =>
+                new WeatherForecast
+                (
+                    DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
+                    Random.Shared.Next(-20, 55),
+                    summaries[Random.Shared.Next(summaries.Length)]
+                ))
+            .ToArray();
+        return forecast;
+    })
+    .WithName("GetWeatherForecast")
+    .WithOpenApi();
+
+app.Run();
+
+record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
+{
+    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
+}

sdk/@launchdarkly/observability-dotnet/AspSampleApp/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

sdk/@launchdarkly/observability-dotnet/AspSampleApp/appsettings.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

sdk/@launchdarkly/observability-dotnet/LaunchDarkly.Observability.sln

@@ -12,6 +12,9 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Docs", "Docs", "{25034066-0
 		README.md = README.md
 	EndProjectSection
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "AspSampleApp", "AspSampleApp\AspSampleApp.csproj", "{84C42307-BD0F-4558-84C5-6E9B06932D8E}"
+EndProject
+
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -29,5 +32,9 @@ Global
 		{85022F8E-D264-44F4-A8AF-1117D8202FBD}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{85022F8E-D264-44F4-A8AF-1117D8202FBD}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{85022F8E-D264-44F4-A8AF-1117D8202FBD}.Release|Any CPU.Build.0 = Release|Any CPU
+		{84C42307-BD0F-4558-84C5-6E9B06932D8E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{84C42307-BD0F-4558-84C5-6E9B06932D8E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{84C42307-BD0F-4558-84C5-6E9B06932D8E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{84C42307-BD0F-4558-84C5-6E9B06932D8E}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

sdk/@launchdarkly/observability-dotnet/src/LaunchDarkly.Observability/LaunchDarkly.Observability.csproj

@@ -1,5 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <!--x-release-please-start-version-->
     <Version>0.0.0</Version>
@@ -35,4 +34,31 @@
     <AssemblyOriginatorKeyFile>../../../../../LaunchDarkly.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
   </PropertyGroup>
+
+  <ItemGroup>
+    <!-- Open Telemetry Dependencies -->
+    <PackageReference Include="OpenTelemetry" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Exporter.Console" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Extensions.Hosting" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.GrpcNetClient" Version="1.12.0-beta.1" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Http" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Process" Version="1.12.0-beta.1" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Quartz" Version="1.12.0-beta.1" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Runtime" Version="1.12.0" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.SqlClient" Version="1.12.0-beta.2" />
+    <PackageReference Include="OpenTelemetry.Instrumentation.Wcf" Version="1.12.0-beta.1" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- LaunchDarkly Dependencies -->
+    <PackageReference Include="LaunchDarkly.ServerSdk" Version="[8.10.0,9.0.0)" />
+    <PackageReference Include="LaunchDarkly.ServerSdk.Telemetry" Version="[1.2.0,2.0.0)" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <!-- Temporary dependency until: https://github.com/open-telemetry/opentelemetry-dotnet/issues/5973 is resolved. -->
+    <PackageReference Include="System.Diagnostics.DiagnosticSource" Version="9.0.0" />
+  </ItemGroup>
 </Project>

sdk/@launchdarkly/observability-dotnet/src/LaunchDarkly.Observability/ObservabilityConfig.cs

@@ -0,0 +1,165 @@
+namespace LaunchDarkly.Observability
+{
+    public struct ObservabilityConfig
+    {
+        /// <summary>
+        /// The configured OTLP endpoint.
+        /// </summary>
+        public string OtlpEndpoint { get; }
+
+        /// <summary>
+        /// The configured back-end URL.
+        /// <para>
+        /// This is used for non-telemetry operations such as accessing the sampling configuration.
+        /// </para>
+        /// </summary>
+        public string BackendUrl { get; }
+        /// <summary>
+        /// The name of the service.
+        /// <para>
+        /// The service name is used for adding resource attributes. If a service name is not defined, then the
+        /// service version will also not be included in the resource attributes.
+        /// </para>
+        /// </summary>
+        public string ServiceName { get; }
+        /// <summary>
+        /// The version of the service.
+        /// </summary>
+        public string ServiceVersion { get; }
+        /// <summary>
+        /// The environment for the service.
+        /// </summary>
+        public string Environment { get; }
+        /// <summary>
+        /// The LaunchDarkly SDK key.
+        /// </summary>
+        public string SdkKey { get; }
+
+        private ObservabilityConfig(
+            string otlpEndpoint,
+            string backendUrl,
+            string serviceName,
+            string environment,
+            string serviceVersion,
+            string sdkKey)
+        {
+            OtlpEndpoint = otlpEndpoint;
+            BackendUrl = backendUrl;
+            ServiceName = serviceName;
+            Environment = environment;
+            ServiceVersion = serviceVersion;
+            SdkKey = sdkKey;
+        }
+
+        /// <summary>
+        /// Create a new builder for <see cref="ObservabilityConfig"/>.
+        /// </summary>
+        /// <param name="sdkKey">The LaunchDarkly SDK key used for authentication and resource attributes.</param>
+        /// <returns>A new <see cref="Builder"/> instance for configuring observability.</returns>
+        internal static Builder CreateBuilder(string sdkKey) => new Builder(sdkKey);
+
+        /// <summary>
+        /// Fluent builder for <see cref="ObservabilityConfig"/>.
+        /// </summary>
+        public sealed class Builder
+        {
+            private const string DefaultOtlpEndpoint = "https://otel.observability.app.launchdarkly.com:4318";
+            private const string DefaultBackendUrl = "https://pub.observability.app.launchdarkly.com";
+            private string _otlpEndpoint = DefaultOtlpEndpoint;
+            private string _backendUrl = DefaultBackendUrl;
+            private string _serviceName = string.Empty;
+            private string _environment = string.Empty;
+            private string _serviceVersion = string.Empty;
+            private readonly string _sdkKey;
+
+            internal Builder(string sdkKey)
+            {
+                this._sdkKey = sdkKey;   
+            }
+
+            /// <summary>
+            /// Set the OTLP endpoint.
+            /// <para>
+            /// For most configurations, the OTLP endpoint will not need to be set.
+            /// </para>
+            /// <para>
+            /// Setting the endpoint to null will reset the builder value to the default.
+            /// </para>
+            /// </summary>
+            /// <param name="otlpEndpoint">The OTLP exporter endpoint URL.</param>
+            /// <returns>A reference to this builder.</returns>
+            public Builder WithOtlpEndpoint(string otlpEndpoint)
+            {
+                _otlpEndpoint = otlpEndpoint ?? DefaultOtlpEndpoint;
+                return this;
+            }
+
+            /// <summary>
+            /// Set the back-end URL for non-telemetry operations.
+            /// <para>
+            /// For most configurations, the backend url will not need to be set.
+            /// </para>
+            /// <para>
+            /// Setting the url to null will reset the builder value to the default.
+            /// </para>
+            /// </summary>
+            /// <param name="backendUrl">The back-end URL used for non-telemetry operations.</param>
+            /// <returns>A reference to this builder.</returns>
+            public Builder WithBackendUrl(string backendUrl)
+            {
+                _backendUrl = backendUrl ?? DefaultBackendUrl;
+                return this;
+            }
+
+            /// <summary>
+            /// Set the service name.
+            /// </summary>
+            /// <param name="serviceName">The logical service name used in telemetry resource attributes.</param>
+            /// <returns>A reference to this builder.</returns>
+            public Builder WithServiceName(string serviceName)
+            {
+                _serviceName = serviceName ?? string.Empty;
+                return this;
+            }
+
+            /// <summary>
+            /// Set the service version.
+            /// </summary>
+            /// <param name="serviceVersion">
+            /// The version of the service that will be added to resource attributes when a service name is provided.
+            /// </param>
+            /// <returns>A reference to this builder.</returns>
+            public Builder WithServiceVersion(string serviceVersion)
+            {
+                _serviceVersion =  serviceVersion ?? string.Empty;
+                return this;
+            }
+
+            /// <summary>
+            /// Set the environment name.
+            /// </summary>
+            /// <param name="environment">The environment name (for example, "prod" or "staging").</param>
+            /// <returns>A reference to this builder.</returns>
+            public Builder WithEnvironment(string environment)
+            {
+                _environment = environment ?? string.Empty;
+                return this;
+            }
+
+            /// <summary>
+            /// Build an immutable <see cref="ObservabilityConfig"/> instance.
+            /// </summary>
+            /// <returns>The constructed <see cref="ObservabilityConfig"/>.</returns>
+            public ObservabilityConfig Build()
+            {
+                return new ObservabilityConfig(
+                    _otlpEndpoint,
+                    _backendUrl,
+                    _serviceName,
+                    _environment,
+                    _serviceVersion,
+                    _sdkKey);
+            }
+        }
+    }
+}