Sample: MultiTenantSaaS

Scenario

You run a multi-tenant SaaS API.
Every call must preserve tenant identity, correlation IDs, and user metadata across downstream services.

Why this matters

• tenant leakage is a security risk
• correlation loss hurts incident debugging
• repeated manual header code causes drift between services

Context contract

public sealed class UserContext
{
    public required string TenantId { get; set; }
    public required string TraceId { get; set; }
    public string? UserId { get; set; }
}

Registration

builder.Services.AddContextR(ctx =>
{
    ctx.Add<UserContext>(reg => reg
        .Map(m => m
            .ByConvention()
            .Property(c => c.TenantId, "X-Tenant-Id")
            .Property(c => c.TraceId, "X-Trace-Id")
            .Property(c => c.UserId, "X-User-Id").Optional())
        .UseAspNetCore(o => o.Enforcement(e =>
        {
            e.Mode = ContextIngressEnforcementMode.FailRequest;
            e.OnFailure = _ => ContextIngressFailureDecision.Fail(400, "Tenant context is required.");
        }))
        .UseGlobalHttpPropagation());
});

Flow

1. API middleware extracts incoming headers into UserContext.
2. Business services consume IContextSnapshot (not raw HttpContext).
3. Outgoing HttpClient propagation writes mapped headers to downstream calls.
4. Missing required fields fail fast or follow custom failure policy.

Suggested integration tests

• request with all headers propagates unchanged to downstream service
• missing X-Tenant-Id is rejected (required)
• missing optional X-User-Id still succeeds
• parallel requests with different tenants remain isolated