This skill detects your .NET application type and instrumentation state, then guides you through the correct setup, migration, or enhancement path.
Step 1 — Detect Application Type
Find all .csproj files (also .fsproj, .vbproj) in the workspace. If multiple non-library projects exist, ask the user which one to instrument before proceeding. Also check for global.json as a .NET workspace indicator.
First, check the <Project Sdk="..."> attribute in the .csproj:
SDK-style projects (modern format — has Sdk attribute)
Signal
App Type
Sdk="Microsoft.NET.Sdk.Web"
ASP.NET Core
Sdk="Microsoft.NET.Sdk.Worker"
Worker Service
Microsoft.Azure.Functions.Worker or Microsoft.NET.Sdk.Functions in PackageReference
Azure Functions — not supported by this skill; refer to Azure Functions monitoring docs
Sdk="Microsoft.NET.Sdk" with <OutputType>Exe</OutputType>
Console App
Sdk="Microsoft.NET.Sdk" with <OutputType>Library</OutputType> or no OutputType
Library — does not get pipeline setup (no AddApplicationInsightsTelemetry() / UseAzureMonitor()), but may need migration if it uses TelemetryClient, ITelemetryInitializer, ITelemetryProcessor, or other 2.x APIs. Check for existing Application Insights package references and apply migration guidance if found.
For ASP.NET Core / Worker Service, read (or in older projects) to confirm hosting pattern:
Program.cs
Startup.cs
WebApplication.CreateBuilder → ASP.NET Core minimal APIs
Host.CreateDefaultBuilder or Host.CreateApplicationBuilder → Generic Host
CreateWebHostBuilder / WebHost.CreateDefaultBuilder → Legacy ASP.NET Core host
Legacy projects (no Sdk attribute — old .csproj format)
If the <Project> element has no Sdk attribute, this is a legacy .NET Framework project. Detect the type using file and reference patterns:
Signal (ANY ONE is sufficient)
App Type
Web.config with <system.web> section
ASP.NET Classic
System.Web in assembly references (<Reference Include="System.Web" />)
ASP.NET Classic
Microsoft.AspNet.* packages in packages.config
ASP.NET Classic
.svc files OR System.ServiceModel reference OR [ServiceContract] attributes
WCF Service — not supported by this skill; manual onboarding required
Microsoft.Owin or Owin in packages.config, or IAppBuilder/IOwinContext usage
OWIN App — not supported by this skill; manual onboarding required
<OutputType>Exe</OutputType> or <OutputType>WinExe</OutputType> with no web signals
Console App
For ASP.NET Classic, further sub-type (all use the same setup):
Microsoft.AspNet.Mvc package + Controllers/ folder → ASP.NET MVC
.aspx or .ascx files → ASP.NET WebForms
Otherwise → ASP.NET Classic (generic)
Entry point: ASP.NET Classic uses Global.asax.cs as its entry point (not Program.cs).
Step 2 — Detect Existing Instrumentation
Check multiple sources for evidence of existing instrumentation:
Source 1 — Package references: Scan PackageReference nodes in .csproj (check both Version and VersionOverride attributes for central package management). For legacy projects, scan <package> elements in packages.config. Version check: major version ≥ 3 → target version; handles wildcards (3.*), pre-release suffixes, and v prefix.
Source 2 — Config files: Check for applicationinsights.config (its presence indicates existing Classic SDK). Scan appsettings*.json for InstrumentationKey or ApplicationInsights sections.
Azure.Monitor.OpenTelemetry.AspNetCore or Azure.Monitor.OpenTelemetry.Exporter
any
Azure Monitor Distro — not covered by this skill. This skill covers Application Insights 3.x SDK only. Inform the user and refer to Azure Monitor OpenTelemetry Distro documentation.
Microsoft.ApplicationInsights.AspNetCore
≥ 3.0
Already on 3.x → go to Enhancement
Microsoft.ApplicationInsights.AspNetCore
< 3.0
Brownfield 2.x → go to Migration
Microsoft.ApplicationInsights.WorkerService
≥ 3.0
Already on 3.x → go to Enhancement
Microsoft.ApplicationInsights.WorkerService
< 3.0
Brownfield 2.x → go to Migration
Microsoft.ApplicationInsights.Web
≥ 3.0
Already on 3.x → go to Enhancement
Microsoft.ApplicationInsights.Web
< 3.0
Brownfield 2.x → go to Migration
Microsoft.ApplicationInsights (base only)
≥ 3.0
Already on 3.x → go to Enhancement
Microsoft.ApplicationInsights (base only)
< 3.0
Brownfield 2.x → go to Migration (Console path)
OpenTelemetry / OpenTelemetry.Api / OpenTelemetry.Extensions.Hosting only (no AI SDK)
any
OpenTelemetry only → go to Enhancement (add Azure Monitor exporter)
If the scan finds NO code changes needed (only unchanged properties used, no removed APIs), the migration is just a package upgrade — read references/no-code-change-migration.md. Note: this path does NOT apply to Classic ASP.NET — Classic always requires config changes.
Classic ASP.NET migration extras: In addition to the references above, Classic ASP.NET brownfield migration requires:
Rewrite applicationinsights.config to 3.x format: remove <TelemetryInitializers>, <TelemetryModules>, <TelemetryProcessors>, <TelemetryChannel> sections; replace <InstrumentationKey> with <ConnectionString>
Update Web.config: remove TelemetryCorrelationHttpModule; verify ApplicationInsightsHttpModule and TelemetryHttpModule are present in <system.webServer><modules>
Replace TelemetryConfiguration.Active with TelemetryConfiguration.CreateDefault()
Connection string goes in ApplicationInsights.config<ConnectionString> element (not appsettings.json)
Use config.ConfigureOpenTelemetryBuilder(otel => ...) for all extensibility (DI-based methods are not available)
Enhancement (Already on 3.x)
Ask the user what they want to add, then read the relevant reference.
DI vs Non-DI: The enhancement references show DI patterns (builder.Services.Configure*). For Console or Classic ASP.NET apps that use TelemetryConfiguration directly, replace builder.Services.ConfigureOpenTelemetryTracerProvider(tracing => ...) with config.ConfigureOpenTelemetryBuilder(otel => otel.WithTracing(tracing => ...)). Each reference file includes a "Non-DI Usage" section.
Learn first, act second: Always read the relevant concept or migration reference BEFORE making code changes.
Connection string, not instrumentation key: Always use ConnectionString, never InstrumentationKey. The environment variable is APPLICATIONINSIGHTS_CONNECTION_STRING. For Classic ASP.NET, connection string goes in ApplicationInsights.config, not appsettings.json.
Application Insights 3.x SDK only: This skill covers Microsoft.ApplicationInsights.AspNetCore / .WorkerService / .Web. The Azure Monitor OpenTelemetry Distro (Azure.Monitor.OpenTelemetry.AspNetCore) is a separate product — do not mix them, and do not use this skill for Distro-based apps.
Classic ASP.NET uses Package Manager Console: Use Install-Package in Visual Studio, not dotnet add package.
Verify after changes: Build the project, run it, and confirm telemetry appears in Azure Portal (Live Metrics for immediate feedback, Transaction Search for 2-5 minute delayed data).
Unsupported app types: If the detected type is WCF Service, OWIN App, or Azure Functions, inform the user that automated setup is not available and point them to the Azure Monitor documentation for manual onboarding.
Error handling: If no .csproj/.fsproj/.vbproj files are found, report that no .NET project was detected rather than guessing.
Examples
Example queries that should use this skill:
"Add Application Insights to my app"
"Set up Azure Monitor telemetry"
"Add observability to my ASP.NET Core project"
"Migrate from Application Insights 2.x to 3.x"
"Upgrade my Application Insights SDK"
"I'm getting deprecated API warnings from Application Insights"
"Add Redis monitoring to my app that already has Application Insights"
"How do I add Entity Framework telemetry"
"Set up OTLP exporter alongside Application Insights"
Troubleshooting
No telemetry appearing: Check that APPLICATIONINSIGHTS_CONNECTION_STRING is set or connection string is configured in appsettings.json. Verify the app targets net8.0 or later for ASP.NET Core 3.x packages.
Package version conflicts: Ensure all Microsoft.ApplicationInsights.* packages are on the same major version. Do not mix 2.x and 3.x packages.
Build errors after migration: Check for removed APIs listed in references/code-migration.md. Common: InstrumentationKey property, ITelemetryInitializer, ITelemetryProcessor, TrackPageView.
