c# - 拦截 C# HttpClient GetAsync

Question

我有一个 Web 项目（C#、MVC5 但没有 WebAPI）和一个简单的 HTTP REST 客户端，它调用外部 REST 服务并获取 accessToken 等。

我想检查我的所有 Get/PostAsync 调用对 statusCode 401 的响应，但我发现我只能SendAsync在实现DelegatingHandler.

class CustomDelegatingHandler : DelegatingHandler
{
    async protected override Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, CancellationToken cancellationToken)
    {
        HttpResponseMessage response = await base.SendAsync(request, cancellationToken);

        if (response.StatusCode == HttpStatusCode.Unauthorized)
        {

还有什么我可以做的，以免改变我所有异步调用的实现SendAsync吗？

（我真正想做的是刷新 accessToken。）

Answer 1

我认为你在正确的轨道上。不过，您不需要将调用更改为 useSendAsync而不是GetAsync,PostAsync等。相反，您需要更改实例化方式HttpClient：

var client = new HttpClient(new CustomDelegatingHandlerTokenRefresher());
// GetAsync, PostAsync, etc will hit your handler

Answer 2

使用装饰器或拦截器模式。

示例混凝土装饰器：

public class CustomDelegatingHandlerTokenRefresher() : DelegatingHandler
{
    public CustomDelegatingHandlerTokenRefresher(DelegatingHandler handler)
    {
        InnerHandler = handler;
    }

    protected override async Task<HttpResponseMessage> SendAsync(
      HttpRequestMessage request, CancellationToken cancellationToken)
    {
        RefreshToken();
        return await InnerHandler.SendAsync(request, cancellationToken);
    }
}