DelegatingHandler中的会话

Question

我已经使用DelegatingHandler作为基类创建了反向代理。它将用于将请求从我们的MVC Web应用程序发送到在我们的本地域中运行的供应商的REST服务。

为了验证请求没有被篡改，我们需要检查一些变量并将它们与Session中存储的值进行比较。

但是，似乎与此相关的HttpRequestMessage request和HttpContextBase都没有可用的会话变量。

RouteTable.Routes.MapHttpRoute(
    name: "ProxyRoute",
    routeTemplate: "/api/proxy/{*path}",  
    handler: HttpClientFactory.CreatePipeline(
        innerHandler: new HttpClientHandler(),
        handlers: new DelegatingHandler[] { new ProxyHandler() }),
    defaults: null,
    constraints: null
);

public class CheckoutProxyHandler : DelegatingHandler
{
    private static HttpClient client = new HttpClient();

    protected override async Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request,
        CancellationToken cancellationToken)
    {
        //Modify some headers here, change Uri...

        var session = ???

        var response = await client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);
        return response;
    }
}

有什么办法可以迫使Asp.Net PipeLine在DelegatingHandler内部提供一个（只读）会话状态？