Intercept 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。

我想检查我对statusCode 401的所有Get/PostAsync调用的响应，但我发现在实现DelegatingHandler时只能覆盖SendAsync方法。

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)
        {

我还可以做些什么来避免将所有异步调用的实现更改为使用SendAsync

(我真正想做的是刷新accessToken。)

Answer 1

我认为你在正确的轨道上。你不需要改变你的调用来使用SendAsync而不是GetAsync，PostAsync等等。相反，您需要更改实例化HttpClient的方式

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。

混凝土装饰器示例：

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);
    }
}