ASP.NET Core CORS WebAPI：无访问-控制-允许-起源头

Question

我已经将我的ASP.NET核心web API部署到Azure上，我可以使用Swagger或像Fiddler这样的web调试器访问它的endpoint。在这两种情况下（在Swagger中使用相同的来源，在我的计算机中使用Fiddler使用不同的来源），当访问API时，我会得到预期的结果，在我的startup.cs中启用CORS如下所示：

>

添加services.addcors()；到configureservices。

public void Configure(IApplicationBuilder app, IHostingEnvironment env, 
    ILoggerFactory loggerFactory,
    IDatabaseInitializer databaseInitializer)
{
    loggerFactory.AddConsole(Configuration.GetSection("Logging"));
    loggerFactory.AddDebug();
    loggerFactory.AddNLog();

    // to serve up index.html
    app.UseDefaultFiles();
    app.UseStaticFiles();

    // http://www.talkingdotnet.com/aspnet-core-diagnostics-middleware-error-handling/
    app.UseDeveloperExceptionPage();
    app.UseDatabaseErrorPage();

    // CORS
    // https://docs.asp.net/en/latest/security/cors.html
    app.UseCors(builder =>
            builder.WithOrigins("http://localhost:4200", "http://www.myclientserver.com")
                .AllowAnyHeader()
                .AllowAnyMethod());

    app.UseOAuthValidation();
    app.UseOpenIddict();
    app.UseMvc();

    databaseInitializer.Seed().GetAwaiter().GetResult();
    env.ConfigureNLog("nlog.config");

    // swagger
    app.UseSwagger();
    app.UseSwaggerUi();
}

使用Fiddler，我可以成功地访问远程API，但没有获得access-control-allog-origin标头。因此，当从浏览器（通过我的客户端应用程序）调用API时，AJAX请求失败，即使服务器返回200。样例Fiddler请求（成功）：

GET http://mywebapisiteurl/api/values HTTP/1.1
User-Agent: Fiddler

回应：

HTTP/1.1 200 OK
Transfer-Encoding: chunked
Content-Type: application/json; charset=utf-8
Server: Microsoft-IIS/8.0
X-Powered-By: ASP.NET
Set-Cookie: ARRAffinity=3d551180c72208c1d997584c2b6119cf44e3a55c868f05ffc9258d25a58e95b1;Path=/;Domain=prinapi.azurewebsites.net
Date: Thu, 01 Dec 2016 10:30:19 GMT

["value1","value2"]

当试图访问部署在Azure上的远程API时，我的客户端应用程序总是以错误的方式失败其AJAX请求：

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://www.myclientserver.com' is therefore not allowed access.

import {Component, NgModule} from '@angular/core';
import {BrowserModule} from '@angular/platform-browser';
import { Http, Headers, Response } from '@angular/http';
import { HttpModule } from '@angular/http';

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Hello {{name}}</h2>
      <button (click)="test()">test</button>
    </div>
  `,
})
export class App {
  name:string;
  constructor(private _http: Http) {
    this.name = 'Angular2'
  }
  public test() {
    this._http.get('http://theapisiteurlhere/api/values',
    {
        headers: new Headers({
          'Content-Type': 'application/json'
        })
    })
    .subscribe(
      (data: any) => {
        console.log(data);
      },
      error => {
        console.log(error);
      });
  }
}

@NgModule({
  imports: [ BrowserModule, HttpModule ],
  declarations: [ App ],
  bootstrap: [ App ]
})
export class AppModule {}

GET http://theapiserver/api/values HTTP/1.1
User-Agent: Fiddler
Host: theapiserver
Origin: http://theappserver/apps/prin

HTTP/1.1 200 OK
Content-Type: application/json; charset=utf-8
Server: Microsoft-IIS/8.0
Access-Control-Allow-Origin: http://theappserver/apps/prin
X-Powered-By: ASP.NET
Set-Cookie: ARRAffinity=3d551180c72208c1d997584c2b6119cf44e3a55c868f05ffc9258d25a58e95b1;Path=/;Domain=theapiserver
Date: Thu, 01 Dec 2016 14:15:21 GMT
Content-Length: 19

["value1","value2"]

来自Angular2(Plunker)的请求/响应反而失败了，正如所报告的那样。通过检查网络流量，我只能看到飞行前请求：

OPTIONS http://theapiserver/api/values HTTP/1.1
Host: theapiserver
Proxy-Connection: keep-alive
Access-Control-Request-Method: GET
Origin: http://run.plnkr.co
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36
Access-Control-Request-Headers: content-type
Accept: */*
Referer: http://run.plnkr.co/h17wYofXGFuTy2Oh/
Accept-Encoding: gzip, deflate, sdch
Accept-Language: en-US,en;q=0.8,it;q=0.6

HTTP/1.1 204 No Content
Server: Microsoft-IIS/8.0
X-Powered-By: ASP.NET
Set-Cookie: ARRAffinity=3d551180c72208c1d997584c2b6119cf44e3a55c868f05ffc9258d25a58e95b1;Path=/;Domain=theapiserver
Date: Thu, 01 Dec 2016 14:23:02 GMT

在此之后，请求失败，没有更多的通信流到服务器。报告的问题是对飞行前请求的响应没有通过访问控制检查，这也是因为响应中缺少标头：

XMLHttpRequest cannot load http://theapiserver/api/values. Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://run.plnkr.co' is therefore not allowed access.

Answer 1

以下是我自己的问题的答案，从评论中复制过来：我没有注意到在Azure portal中有一个CORS部分。如果我不在那里输入任何允许的原点，我的基于代码的配置似乎完全不相关。在我看来，这很奇怪，因为我不得不在这里复制URL，但是一旦我将*添加到允许的起源中，它就起作用了。