application-insights-dotnet

# Application Insights for .NET Agent adds Azure Monitor Application Insights telemetry to .NET apps. Agent verifies signal quality, correlation, and cost controls. ## When to Use | User prompt | Use | |---|---| | User asks for request, dependency, or exception telemetry | Use this skill | | User asks for custom business events or metrics | Use this skill | | User asks for Kusto validation of telemetry flow | Use this skill | ## When Not to Use | User prompt | Route | |---|---| | User asks for a different observability backend only | Use that backend workflow | | User asks for local logging only | Use logging guidance | | User asks for vendor-neutral tracing only | Use `configuring-opentelemetry-dotnet` | ## Required Inputs | Input | Required | Notes | |---|---|---| | Host type | Yes | Web app, API, worker, WebJob, or desktop host. | | Connection string | Yes | Load from configuration or environment. | | Custom signal plan | No | List events, metrics, or traces beyond auto-collection. | | Sampling plan | Recommended | Define cost and fidelity targets. | | Correlation plan | Recommended | Align with `Activity` and structured logging. | ## Workflow | Step | Agent action | Test | Pass | |---|---|---|---| | 1 | Agent installs the host-appropriate SDK package. | Inspect project file. | Package matches the host type. | | 2 | Agent reads the connection string from secure configuration. | Inspect config source. | No hard-coded connection string exists. | | 3 | Agent registers telemetry services. | Inspect startup code. | Automatic request and dependency telemetry are enabled. | | 4 | Agent adds custom events or metrics only for real business signals. | Review `TelemetryClient` usage. | Custom telemetry names are stable and meaningful. | | 5 | Agent adds initializers or processors for common context. | Inspect registrations. | Environment, ring, or tenant metadata flows consistently. | | 6 | Agent configures sampling or filtering. | Review telemetry config. | Noise decreases without hiding important failures. | | 7 | Agent validates Kusto visibility and correlation. | Run query playbook. | Requests, dependencies, and exceptions join correctly. | ## Pattern Matrix | Need | Preferred pattern | |---|---| | ASP.NET Core auto-collection | `AddApplicationInsightsTelemetry(...)` | | Business event | `TelemetryClient.TrackEvent(...)` | | Business metric | `TelemetryClient.GetMetric(...).TrackValue(...)` | | Stable dimensions | `ITelemetryInitializer` | | Cost control | Adaptive sampling or processor filters | | Correlation | Preserve `Activity` context | ## Query Matrix | Goal | Minimal Kusto pattern | |---|---| | Request count and latency | `requests | summarize count(), avg(duration) by name, success` | | Exceptions by type | `exceptions | summarize count() by type` | | Dependency failures | `dependencies | where success == false` | | Correlated trace | Filter by `operation_Id` across tables | ## Validation Checklist - [ ] Agent used configuration-driven connection strings. - [ ] Agent enabled automatic request, dependency, and exception collection for the host. - [ ] Agent added only stable, business-meaningful custom telemetry. - [ ] Agent configured sampling or filtering intentionally. - [ ] Agent preserved `Activity`-based correlation. - [ ] Agent validated telemetry with real Kusto queries.