• Update OpenTelemetry core packages to 1.19.1, instrumentation packages to 1.19.0, and Azure Monitor OpenTelemetry Exporter to 1.10.0.
• Breaking change: Reduce default HTTP client metric volume in ASP.NET Core and Worker Service on .NET 8+ while retaining request latency, count, and failure dimensions through http.client.request.duration. Other System.Net.Http metrics are now opt-in through OpenTelemetry AddView; dashboards and alerts using them must explicitly enable collection. HTTP dependency tracing and server metrics are unchanged. No new public API is introduced. Addresses the HTTP metric-volume concern in #3192.
• Fix #3197: NullReferenceException when using TelemetryClient APIs when no connection string is provided.
• Fix #3211: TelemetryClient.TrackDependency(DependencyTelemetry) and TelemetryClient.TrackRequest(RequestTelemetry) now default an unset Timestamp to DateTimeOffset.UtcNow (restoring 2.x behavior) instead of emitting 0001-01-01T00:00:00Z, which ingestion rejects.
• Fix #3223: The WEB package's activity processors now write the tag keys the Azure Monitor exporter maps (enduser.pseudo.id, microsoft.session.id, microsoft.synthetic_source, microsoft.user.account_id), so user_Id, session_Id, operation_SyntheticSource and user_AccountId are populated again instead of the values landing in customDimensions as ai.user.id, session.id, ai.operation.syntheticSource and enduser.account. user_AccountId is also no longer skipped when the authenticated user cookie is present, and the unmapped session.isFirst custom dimension is no longer emitted.
• Fix StartOperation/StopOperation losing or misreporting telemetry fields. Stopping an operation now exports the fields set on its telemetry item using the same keys as TrackDependency/TrackRequest: dependency Type, Data, Target and ResultCode (previously wrong or empty for HTTP, SQL, Queue Message and custom types), request Url, Source and ResponseCode, Success, and custom Properties. The unmapped OperationName and messaging.destination tags no longer appear as custom dimensions.

Version 3.1.2

• Fix HttpException: Request is not available in this context in the WEB package when calling TrackDependency from Application_Start in classic ASP.NET. The WEB activity processors now safely handle the case where HttpContext.Request is not yet available.
• Fix #3163: TelemetryConfiguration.CreateDefault() on classic ASP.NET now returns a configuration already populated from ApplicationInsights.config (connection string, sampling, storage, live metrics, request/dependency tracking, etc.). A new PreApplicationStartMethod (WebApplicationInsightsInitializer) materializes and populates the singleton before Application_Start runs, so customer code calling TelemetryConfiguration.CreateDefault() from Global.asax.cs no longer gets an empty configuration. The ApplicationInsightsHttpModule no longer carries the config-reading bookkeeping. TelemetryConfiguration.PrependOpenTelemetryBuilderConfiguration no longer throws if the configuration was already built — it silently skips, so a second TelemetryClient constructed against an already-built configuration no longer throws InvalidOperationException.

Version 3.1.1

• Update OpenTelemetry and Azure Monitor dependencies to address known security advisories (e.g. GHSA-g94r-2vxg-569j in OpenTelemetry.Api 1.15.1): #3174
  • OpenTelemetry 1.15.3
  • OpenTelemetry.Exporter.Console 1.15.3
  • OpenTelemetry.Exporter.InMemory 1.15.3
  • OpenTelemetry.Extensions.Hosting 1.15.3
  • OpenTelemetry.Instrumentation.AspNetCore 1.15.2
  • OpenTelemetry.Instrumentation.AspNet 1.15.2
  • OpenTelemetry.Instrumentation.Http 1.15.1
  • OpenTelemetry.Instrumentation.SqlClient 1.15.2
  • Azure.Monitor.OpenTelemetry.Exporter 1.8.0

Version 3.1.0

• Make TelemetryContext properties public and propagate them via TelemetryClient.
• Add fallback to APPLICATIONINSIGHTS_CONNECTION_STRING environment variable for Base, Web, and NLog packages when connection string is not set via code.
• Update Azure.Monitor.OpenTelemetry.Exporter to 1.7.0. This includes updated mappings for telemetry context.
• Fix OTEL_SDK_DISABLED not being honored when TelemetryConfiguration.DisableTelemetry is set in DI scenarios., #3157
• Fix TrackAvailability ignoring user-specified Timestamp on AvailabilityTelemetry. The timestamp is now emitted as microsoft.availability.testTimestamp so downstream exporters can use the correct event time.
• Added netstandard2.0 target framework to Microsoft.ApplicationInsights package to support customers with shared libraries targeting netstandard2.0.
• Fix TelemetryClient.Context.Cloud.RoleName set after construction now applies to all telemetry.
• Fix bug where Debug/Trace level logs from TrackTrace API were not emitted to Application Insights
• Fix Track API calls to not mutate the passed in dictionary if it is readonly
• Fix NullReferenceException in TelemetryClient.Flush() and FlushAsync() when called from DI scenarios
• Fix ApplicationVersion ignored: ApplicationInsightsServiceOptions.ApplicationVersion is now applied as service.version on the OpenTelemetry Resource for both AspNetCore and WorkerService packages
• Fix HttpRequestExtensions.UnvalidatedGetHeader always returning empty string instead of the actual header value. Restored max-length enforcement to guard against oversized header values.

• Replaced netstandard2.0 with net8.0 target framework in Microsoft.ApplicationInsights.NLogTarget package.

• Removed netstandard2.0 target framework from Microsoft.ApplicationInsights, Microsoft.ApplicationInsights.AspNetCore, and Microsoft.ApplicationInsights.WorkerService packages.
• The JavaScript in Microsoft.ApplicationInsights.AspNetCore has been updated to version 10.
• Centralized package version management
• Update OpenTelemetry dependencies, #3092
  • OpenTelemetry 1.15.0
  • OpenTelemetry.Instrumentation.AspNetCore 1.15.0
  • OpenTelemetry.Instrumentation.AspNet 1.15.1
  • OpenTelemetry.Instrumentation.Http 1.15.0
  • OpenTelemetry.Instrumentation.SqlClient 1.15.0
• Vendored OpenTelemetry.Resources.Azure resource detectors to NETCORE shared folder, replaced package with vendored implementation, #3093
• Added support to disable telemetry via TelemetryConfiguration.DisableTelemetry
• Removed EnabledAdaptiveSampling and replaced with TracesPerSecond and SamplingRatio
• Added EnableTraceBasedLogsSampler property to ApplicationInsightsServiceOptions for ASP.NET Core and WorkerService packages
• Added support for StorageDirectory and DisableOfflineStorage from TelemetryConfiguration in DI scenarios
• Update Azure.Monitor.OpenTelemetry.Exporter dependency to 1.6.0

Added

• Automatic configuration binding from "ApplicationInsights" section in appsettings.json for both AspNetCore and WorkerService packages with configuration precedence: environment variables > explicit configuration > appsettings.json
• Added support for Entra ID (Azure Active Directory) authentication using Azure.Core.TokenCredential
• Added Self Diagnostics feature
• Updated the default sampler from Fixed Rate to Rate-Limited Sampling.
• Update Azure Monitor Exporter to 1.6.0-beta.2
• Add comprehensive applicationinsights.config support
• Add properties in TelemetryConfiguration to configure underlying exporter

Bug fix

• Fix TrackMetric(MetricTelemetry) unsupported telemetry type error

• The following Application Insights packages in this repo now use OpenTelemetry internally. OpenTelemetry is the industry standard for telemetry collection and provides better interoperability with other observability tools.
  • Microsoft.ApplicationInsights
  • Microsoft.ApplicationInsights.AspNetCore
  • Microsoft.ApplicationInsights.WorkerService
  • Microsoft.ApplicationInsights.Web
  • Microsoft.ApplicationInsights.NLogTarget
• Classic APIs of the above packages are preserved; calls are translated to OpenTelemetry telemetry.
• Other packages not listed above (such as certain auto-collectors and logging adapters that were published from this repo previously) will not have future versions published. See BreakingChanges.md for details.

• no changes since beta.

• Populate required field Message with "n/a" if it is empty
• Fix ITelemetryModule singleton registration to support presence of keyed services