C# 在windows窗体的HttpClient类中使用DelegatingHandler-尚未设置内部处理程序

首先，我收到的错误消息如下：尚未设置内部处理程序

我正在编写一个自定义消息处理程序来处理API的身份验证cookie超时。例如，如果我的代码库调用API，然后又收到401，那么它应该重试登录url以获得更新的cookie。我计划按如下方式完成这项工作：

public class CkApiMessageHandler : DelegatingHandler
{
    private readonly string _email;
    private readonly string _password;
    private const string _loginPath = "Account/Login";

    public CkApiMessageHandler(string email, string password)
    {
        _email = email;
        _password = password;

        //InnerHandler = new HttpControllerDispatcher(null);
    }

    protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {

        var response = await base.SendAsync(request, cancellationToken);

        if(response.StatusCode == System.Net.HttpStatusCode.Unauthorized)
        {
            Logging.Logger.LogInformation("Authentication cookie timed out");
            var baseAddress = request.RequestUri.Host;
            var loginPath = baseAddress + _loginPath;

            var originalRequest = request;

            var loginRequest = new HttpRequestMessage(new HttpMethod("POST"), loginPath);
            var dict = new Dictionary<string, string>();
            dict.Add("Email", _email);
            dict.Add("Password", _password);

            var form = new FormUrlEncodedContent(dict);
            loginRequest.Content = form;
            loginRequest.Headers.Clear();

            foreach(var header in originalRequest.Headers)
            {
                loginRequest.Headers.Add(header.Key, header.Value);
            }

            var loginResponse = await base.SendAsync(loginRequest, cancellationToken);

            if (loginResponse.IsSuccessStatusCode)
            {
                Logging.Logger.LogInformation("Successfully logged back in");
                return await base.SendAsync(originalRequest, cancellationToken);
            }
            else
            {
                Logging.Logger.LogException(new Exception("Failed to log back in"), "Could not log back in");
            }
        }

        return response;
    }


}  

所以我的问题是：如何让这个DelegatingHandler在web api项目的上下文之外完成它的工作

正在进行更新。看起来我可以只使用HttpClientHandler类

---

我应该早点意识到这一点，但是将内部处理程序设置为

HttpClient

使用的默认处理程序是有意义的。因此，在

DelegatingHandler

的子类中，您应该将内部处理程序设置为

HttpClient

使用的默认处理程序，如下所示：

    public CkApiMessageHandler(string email, string password, Guid moduleId)
    {
        _email = email;
        _password = password;
        _moduleId = moduleId;
        InnerHandler = new HttpClientHandler();

    }

---

或者您可以使用HttpClientFactory

_client  = HttpClientFactory.Create(new CKEnterprise.Common.CkApiMessageHandler(email, password))

---

阿德里安的回答是正确的。您必须为自定义处理程序设置内部处理程序，但是有更好的方法来设置内部处理程序

public MyDelegatingHandler( ) : base( new HttpClientHandler( ) )

---

这完全不是直觉。好发现：）这对我来说更有意义。谢谢Raj

_client  = HttpClientFactory.Create(new CKEnterprise.Common.CkApiMessageHandler(email, password))

public MyDelegatingHandler( ) : base( new HttpClientHandler( ) )