Web Api 2处理选项请求

Question

我在Azure和Web Api 2 forntend上托管了AngularJs后端。据我所知，有些HTTP request使用OPTIONS request进行预检。我的问题是如何以这种方式实现后端，如果在控制器中有一些动作将处理以下OPTIONS requests，所有GET/POST/PUT/DELETE/...将返回200。

Answer 1

解决此任务的非常优雅的方法是手动添加每个控制器

[AcceptVerbs("OPTIONS")]
public HttpResponseMessage Options()
{
    var resp = new HttpResponseMessage(HttpStatusCode.OK);
    resp.Headers.Add("Access-Control-Allow-Origin", "*");
    resp.Headers.Add("Access-Control-Allow-Methods", "GET,DELETE");

    return resp;
}

或覆盖MessageHandlers

 public class OptionsHttpMessageHandler : DelegatingHandler
{
  protected override Task<HttpResponseMessage> SendAsync(
  HttpRequestMessage request, CancellationToken cancellationToken)
  {
    if (request.Method == HttpMethod.Options)
      {
         var apiExplorer = GlobalConfiguration.Configuration.Services.GetApiExplorer();

          var controllerRequested = request.GetRouteData().Values["controller"] as string;              
          var supportedMethods = apiExplorer.ApiDescriptions.Where(d => 
             {  
                var controller = d.ActionDescriptor.ControllerDescriptor.ControllerName;
                return string.Equals(
                    controller, controllerRequested, StringComparison.OrdinalIgnoreCase);
            })
          .Select(d => d.HttpMethod.Method)
          .Distinct();

      if (!supportedMethods.Any())
         return Task.Factory.StartNew(
             () => request.CreateResponse(HttpStatusCode.NotFound));

      return Task.Factory.StartNew(() =>
        {
            var resp = new HttpResponseMessage(HttpStatusCode.OK);
            resp.Headers.Add("Access-Control-Allow-Origin", "*");
            resp.Headers.Add(
                "Access-Control-Allow-Methods", string.Join(",", supportedMethods));

            return resp;
        });
}

return base.SendAsync(request, cancellationToken);

  }
}

然后在配置中

GlobalConfiguration.Configuration.MessageHandlers.Add(new OptionsHttpMessageHandler());

即便是第二种选择并不完美但是......没有原生的支持

Answer 2

我遇到了与你相同的问题，即所谓的Preflight请求，我发现这可能与Web.Conf文件上的配置错误有关。注释掉或删除包含OPTIONSVerbHandler“删除”的行（如果存在）。

<system.webServer>
<handlers>
      <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
      <!--<remove name="OPTIONSVerbHandler" /> -->
      <remove name="TRACEVerbHandler" />
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
</system.webServer>