Sample: HttpContextAccessorReplacement

Goal

Replace direct IHttpContextAccessor usage in application services with explicit ContextR context/snapshot patterns.

Typical anti-pattern

public sealed class PricingService
{
    private readonly IHttpContextAccessor _httpContextAccessor;

    public PricingService(IHttpContextAccessor httpContextAccessor)
    {
        _httpContextAccessor = httpContextAccessor;
    }

    public string? GetTenant()
    {
        return _httpContextAccessor.HttpContext?.Request.Headers["X-Tenant-Id"];
    }
}

Problems:

• tightly coupled to HTTP runtime
• hard to test outside ASP.NET integration tests
• brittle in background tasks and asynchronous fan-out

ContextR replacement

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

builder.Services.AddContextR(ctx =>
{
    ctx.Add<UserContext>(reg => reg
        .MapProperty(c => c.TenantId, "X-Tenant-Id")
        .MapProperty(c => c.TraceId, "X-Trace-Id")
        .MapProperty(c => c.UserId, "X-User-Id")
        .UseAspNetCore()
        .UseGlobalHttpPropagation());
});

public sealed class PricingService
{
    private readonly IContextSnapshot _snapshot;

    public PricingService(IContextSnapshot snapshot)
    {
        _snapshot = snapshot;
    }

    public string? GetTenant()
    {
        return _snapshot.GetContext<UserContext>()?.TenantId;
    }
}

Why snapshot model is useful

• explicit contract instead of magic header reads
• deterministic data view during operation lifetime
• works in non-web and background execution
• easier unit testing without full HTTP stack

Suggested tests

• PricingService unit test with synthetic IContextSnapshot
• integration test proving inbound header extraction still works
• background dispatch test using snapshot.BeginScope()