集成上下文

public sealed class IntegrationContext
{
    public string? TenantId { get; }
    public string? Region { get; }
    public string? Environment { get; }
    public string? CorrelationId { get; }

    // ① With() 返回修改后的副本，原实例不变
    public IntegrationContext With(
        string? tenantId = null,
        string? region = null,
        string? environment = null,
        string? correlationId = null);
}

public interface IIntegrationContextAccessor
{
    IntegrationContext? Current { get; }

    // ① Push 返回 IDisposable，using 块结束时自动恢复上一个上下文
    IDisposable Push(IntegrationContext context);
}

public class TenantMiddleware(IIntegrationContextAccessor contextAccessor) : IMiddleware
{
    public async Task InvokeAsync(HttpContext context, RequestDelegate next)
    {
        // ① 从 HTTP 请求中提取租户和关联 ID
        var tenantId = context.User.FindFirst("tenant_id")?.Value;
        var correlationId = context.TraceIdentifier;

        var integrationContext = new IntegrationContext()
            .With(tenantId: tenantId, correlationId: correlationId);

        // ② Push 到 AsyncLocal 作用域，下游所有 Provider 都能读到
        using (contextAccessor.Push(integrationContext))
        {
            await next(context);
        }
        // ③ using 块结束，上下文自动恢复
    }
}

// Provider 实现中读取上下文
public class PaymentService(
    IPaymentProvider payment,
    IIntegrationContextAccessor contextAccessor)
{
    public async Task PayAsync(PaymentOrderRequest request)
    {
        var ctx = contextAccessor.Current;
        if (ctx?.TenantId is not null)
        {
            // ① 带上租户上下文调用第三方 API
            request.Extra["tenant_id"] = ctx.TenantId;
        }

        await payment.CreateOrderAsync(request);
    }
}