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Microsoft.Extensions.AI

The canonical .NET AI abstraction. Every later piece in this guide — Agent Framework, RAG, function calling, observability — is built on top of IChatClient and friends. Understand this layer first.

Topics (canonical order)

  •   IChatClient & Pipeline

    The contract, the middleware/pipeline pattern, building a custom delegating client

  •   IEmbeddingGenerator

    The embeddings contract, batching, dimensionality, cross-vendor portability

  •   IImageGenerator

    The image-generation contract, prompts, models, output formats

  •   Function Calling — Auto

    FunctionChoiceBehavior.Auto, declaring functions, why auto function calling supersedes deprecated planners

  •   Telemetry & Caching

    Built-in OpenTelemetryMiddleware, distributed tracing of LLM calls, response caching, redaction

Why this order

Contract first (IChatClient), then siblings (embeddings, images), then the killer capability layered on top (function calling), then cross-cutting middleware (telemetry, caching). Each topic depends on the previous.

Cross-references