Tutorials ASP.NET Core with Agentic AI Tutorial

AI Middleware — Complete Guide

AI Middleware — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of ASP.NET Core with Agentic AI Tutorial on Toolliyo Academy.

8 min read Updated 8/3/2026

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ASP.NET Core with Agentic AI Tutorial · Lesson 14 of 100

AI Middleware

AI basics → Agents

AI basics · 1 — Setup · ~6 min · Module 2: ASP.NET Core AI Fundamentals

What is this?

AI middleware sits in the ASP.NET Core pipeline to attach tenant context, enforce quotas, redact PII, or log prompts before controllers run. AgentNest wraps risky endpoints with middleware instead of duplicating checks in every action.

Why should you care?

CRM and ERP APIs share one pipeline; central middleware guarantees token budgets and correlation IDs on every AI call.

See it live — copy this example

Paste into an ASP.NET Core 8+ / AgentNest project, then run with dotnet run (set your API keys in user-secrets).

// AgentNest.Api/Middleware/AiQuotaMiddleware.cs
public sealed class AiQuotaMiddleware(RequestDelegate next, ITenantQuotaService quotas)
{
    public async Task InvokeAsync(HttpContext ctx)
    {
        if (!ctx.Request.Path.StartsWithSegments("/api/ai")) { await next(ctx); return; }
        var tenantId = ctx.User.FindFirst("tenant_id")?.Value ?? "anonymous";
        if (!await quotas.TryConsumeAsync(tenantId, ctx.RequestAborted))
        { ctx.Response.StatusCode = StatusCodes.Status429TooManyRequests; return; }
        await next(ctx);
    }
}

What happened?

Middleware short-circuits /api/ai routes when tenant quota is exhausted.
Non-AI routes pass through untouched, keeping overhead minimal.

Practice next

build ITenantQuotaService backed by Redis or SQL counters.
Register app.UseMiddleware() after UseAuthentication.
Integration-test 429 when quota is zero.
Add X-Correlation-Id header propagation in the same middleware.
Skip quota for internal service accounts with a claim check.

Remember

Middleware centralizes AI policy in the HTTP pipeline. Scope checks to /api/ai paths for performance. Return 429 with clear semantics when quotas fail.