在启动中启用 CORS 失败并出现预检错误

Question

我正在尝试在 Startup.cs 中启用 CORS，但没有成功。我在端口 4200 上有一个 Angular 应用程序，试图与我的 c# Web 应用程序通信。我在 Angular 中不断收到此错误无法加载http://localhost:52008/Account/GetJWT：预检响应没有 HTTP ok 状态。我的研究似乎表明 CORS 未正确启用。知道我错过了什么吗？public void ConfigureServices(IServiceCollection services){.....    services.AddCors(options =>    {        options.AddPolicy("EnableCORS", builder =>        {            builder.AllowAnyOrigin()            .AllowAnyMethod()            .AllowAnyHeader()            .AllowCredentials()            .Build();        });    });    .........}public void Configure(IApplicationBuilder app, IHostingEnvironment env){....... app.UseCors("EnableCORS"); ........ }这是 Angular POST 请求：  login(form: NgForm) {    let credentials = JSON.stringify(form.value);    console.log(credentials);    this.http.post("http://localhost:52008/Account/GetJWT", credentials, {      headers: new HttpHeaders({        "Content-Type": "application/json"      })    })  }POSTMAN 查询的结果

Answer 1

使用以下代码启用 CORS。.NET Core 版本：2.1 和 Angular 版本：1.6.7

public class Startup

{

    public Startup(IConfiguration configuration)

    {

        Configuration = configuration;

    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.

    public void ConfigureServices(IServiceCollection services)

    {

        services.AddMvc()

            .AddJsonOptions(options =>

        {

            options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;

            options.SerializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.None;                

        });

        services.AddCors();

    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.

    public void Configure(IApplicationBuilder app, IHostingEnvironment env, IServiceProvider serviceProvider)

    { 

        app.UseCors(options =>

        {

            options.AllowAnyMethod();

            options.AllowAnyOrigin();

            options.AllowAnyHeader();

        });

        app.UseMvc();

    }   

}

角代码：

$http.post("http://localhost:52008/Account/GetJWT", credentials,{

    headers: new HttpHeaders({

        "Content-Type": "application/json"

})).then(

function(response) {

    console.log(response);

},

function() {

    console.log("unable to login");

});

如果问题仍然存在，请告诉我。

Answer 2

您可以在 startup.cs 中配置核心，如下所示，并将源添加到 ConfigurationServices，如下所示。

public void ConfigureServices(IServiceCollection services)

{

    services.AddCors(options =>

    {

        options.AddPolicy("AllowSpecificOrigin",

            builder => builder.WithOrigins("http://example.com"));

    });

}

public void Configure(IApplicationBuilder app, IHostingEnvironment env, 

    ILoggerFactory loggerFactory)

{

    loggerFactory.AddConsole();

    if (env.IsDevelopment())

    {

        app.UseDeveloperExceptionPage();

    }

    // Shows UseCors with named policy.

    app.UseCors("AllowSpecificOrigin");

    app.Run(async (context) =>

    {

        await context.Response.WriteAsync("Hello World!");

    });

}

将 CORS 策略添加到特定操作。

[HttpGet]

[EnableCors("AllowSpecificOrigin")]

public IEnumerable<string> Get()

{

    return new string[] { "value1", "value2" };

}

Answer 3

    public void ConfigureServices(IServiceCollection services)

        {

           //add cors service

            services.AddCors(options => options.AddPolicy("Cors",

                builder => {

                    builder.AllowAnyOrigin()

                    .AllowAnyMethod()

                    .AllowAnyHeader();

                } ));

            services.AddMvc(); // 

//--------------------------------------

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.

 public void Configure(IApplicationBuilder app, IHostingEnvironment env)

    {

        if (env.IsDevelopment())

        {

            app.UseDeveloperExceptionPage();

        }

        app.UseCors("Cors");//------>let app use new service

        app.UseMvc();

    }

在您的控制器内部，确保您从身体上抓取物体

//发布请求

 [HttpPost]

    public Message Post([FromBody] Message message)

    {

    var msg = new Message { Owner = message.Owner, Text = message.Text };

    db.Messages.AddAsync(msg);

    db.SaveChangesAsync();

    return message;

}