MicroKit.MultiTenancy 1.0.0-preview.2

MicroKit.MultiTenancy

Pluggable multi-tenancy for .NET 10. Per-request immutable TenantContext, startup-time wiring validation, region-aware endpoint routing, composite region resolver chains — and zero third-party dependencies in the Abstractions package.

What makes this production-grade

SetTenant is write-once per scope. TenantContext.SetTenant throws InvalidOperationException if called a second time on the same scoped instance. The middleware resolves the tenant once at the start of the request and sets it. From that point forward, any code that receives ITenantContext gets the same immutable tenant — there is no risk of a handler or background service overwriting the tenant mid-request.

EnsureResolved as a contract. ITenantContext.EnsureResolved() throws if the tenant has not been resolved. Call it at the top of any handler that requires a tenant and get an unambiguous InvalidOperationException instead of a null-reference downstream. This is a first-class API, not a defensive null check scattered across handlers.

Startup-time DI validation. MultiTenantValidationService is an IHostedService that runs IModuleValidator.Validate() for every registered validator during StartAsync. The MultiTenancyModuleValidator checks that ITenantRegistry is registered. If it is missing, the application fails to start with an InvalidOperationException naming the missing service — not a NullReferenceException on the first request.

Composite region resolver. CompositeTenantRegionResolver chains multiple ITenantRegionResolver implementations and returns the first non-null result. Resolvers are tried in registration order. This allows a claim-based resolver to take precedence, with a database-backed resolver as fallback.

Region-aware endpoint routing. RegionAwareTenantEndpointProvider resolves the service endpoint URL for a tenant based on its region — enabling geo-partitioned architectures where each tenant's data lives in a different region and outgoing calls must target the correct regional endpoint.

SkipTenantValidationAttribute for pre-auth endpoints. Decorate a controller or minimal API group with SkipTenantValidationAttribute to exempt it from tenant resolution. This is the correct place to exempt public sign-up, health checks, and OIDC callback endpoints without disabling middleware globally.

Three built-in resolution strategies. HeaderResolutionStrategy reads a configurable header (default: X-Tenant-Id). JwtClaimResolutionStrategy reads a configurable JWT claim. Both are registered as both IHttpTenantResolutionStrategy and ITenantResolutionStrategy, so non-HTTP consumers can resolve the strategy through the base interface.

Installation

# Contracts — ITenant, ITenantContext, ITenantResolutionStrategy — zero deps
dotnet add package MicroKit.MultiTenancy.Abstractions

# TenantContext, region resolvers, startup validator, AddMicroKitMultiTenancy
dotnet add package MicroKit.MultiTenancy

# HTTP resolution strategies, TenantResolutionMiddleware
dotnet add package MicroKit.MultiTenancy.Extensions

# EF Core ITenantStore
dotnet add package MicroKit.MultiTenancy.EFCoreStore

# Redis ITenantCache
dotnet add package MicroKit.MultiTenancy.Redis

Usage

Access the current tenant in a handler

using MicroKit.MultiTenancy.Abstractions;

public sealed class GetDashboardHandler : IQueryHandler<GetDashboardQuery, DashboardDto>
{
    private readonly ITenantContext _tenant;
    private readonly IReadRepository<Order> _orders;

    public GetDashboardHandler(ITenantContext tenant, IReadRepository<Order> orders) =>
        (_tenant, _orders) = (tenant, orders);

    public async Task<DashboardDto> HandleAsync(GetDashboardQuery query, CancellationToken ct)
    {
        // Throws InvalidOperationException with a clear message if not resolved
        _tenant.EnsureResolved();

        var orders = await _orders.FindAsync(
            o => o.TenantId == _tenant.Tenant!.Id, ct);

        return new DashboardDto(orders.Count, _tenant.Tenant!.Name);
    }
}

ITenant contract

Mark an entity as tenant-owned

using MicroKit.MultiTenancy.Abstractions;

public sealed class Invoice : AggregateRoot<Guid>, IHasMultiTenant
{
    public string TenantId { get; private set; } = null!;
    // ... domain fields
}

Use IHasMultiTenant in your EF Core global query filter:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<Invoice>()
        .HasQueryFilter(e => e.TenantId == _tenantContext.TenantId);
}

Custom resolution strategy

using MicroKit.MultiTenancy.Abstractions;

public sealed class SubdomainResolutionStrategy : ITenantResolutionStrategy
{
    private readonly IHttpContextAccessor _http;

    public SubdomainResolutionStrategy(IHttpContextAccessor http) => _http = http;

    public ValueTask<string?> ResolveAsync(CancellationToken ct = default)
    {
        var host = _http.HttpContext?.Request.Host.Host;
        var subdomain = host?.Split('.').FirstOrDefault();
        return new ValueTask<string?>(subdomain);
    }
}

// Registration
builder.Services.AddSingleton<ITenantResolutionStrategy, SubdomainResolutionStrategy>();

Composite region resolver

// Registered via DI — tried in order; first non-null result wins
services.AddScoped<ITenantRegionResolver, ClaimsTenantRegionResolver>();     // first
services.AddScoped<ITenantRegionResolver, DatabaseTenantRegionResolver>();   // fallback
services.AddScoped<ITenantRegionResolver, ConfigurationTenantRegionResolver>(); // last resort

// CompositeTenantRegionResolver is registered automatically by AddMicroKitMultiTenancy

Configuration

using MicroKit.MultiTenancy.Extensions;

builder.Services
    .AddMicroKitMultiTenancy(options =>
    {
        options.HeaderName            = "X-Tenant-Id";  // used by WithHeaderStrategy
        options.ClaimNames            = "tenant_id";    // used by WithJwtClaimStrategy
        options.EnableValidationWorker = true;           // run IModuleValidator on startup
    })
    .WithHeaderStrategy()       // reads X-Tenant-Id header; override header name in options
    // .WithJwtClaimStrategy()  // reads tenant_id JWT claim; override claim name in options
    .WithRedisCache(opts =>
    {
        opts.ConnectionString = "localhost:6379";
        opts.KeyPrefix        = "tenant:";
        opts.Expiry           = TimeSpan.FromMinutes(15);
    });

var app = builder.Build();

// Resolves the tenant for every request and calls TenantContext.SetTenant once
app.UseMultiTenancy();

appsettings.json

{
  "MicroKit": {
    "MultiTenancy": {
      "HeaderName": "X-Tenant-Id",
      "ClaimNames": "tenant_id",
      "EnableValidationWorker": true
    }
  }
}

Skip tenant resolution for specific endpoints

using MicroKit.MultiTenancy.Attributes;

[SkipTenantValidation]
[ApiController]
[Route("health")]
public class HealthController : ControllerBase
{
    [HttpGet] public IActionResult Get() => Ok();
}

Key types

Package dependency graph

MicroKit.MultiTenancy.Abstractions
    MicroKit.Abstractions
    (no third-party NuGet dependencies)

MicroKit.MultiTenancy
    MicroKit.MultiTenancy.Abstractions
    Microsoft.Extensions.Caching.Memory
    Microsoft.Extensions.Hosting

MicroKit.MultiTenancy.Extensions
    MicroKit.MultiTenancy
    Microsoft.AspNetCore.Http

MicroKit.MultiTenancy.EFCoreStore
    MicroKit.MultiTenancy
    Microsoft.EntityFrameworkCore

MicroKit.MultiTenancy.Redis
    MicroKit.MultiTenancy
    StackExchange.Redis