ASP.NET CORS

CORS(Cross-Origin Resource Sharing)是由W3C指定的标准，其目的是帮助在各个站点间的资源共享。实现跨域资源共享。
在.NETCore中，可以通过以下三种方式启用CORS
1.使用默认策略/命名策略的中间件的方式

private readonly string CORS_ALLOW_ORGINS = "cors_allow_orgins";

public void ConfigureServices(IServiceCollection services)
{
    services.AddCors(options =>
    {
        options.AddPolicy(CORS_ALLOW_ORGINS, policy =>
        {
            policy.WithOrigins("http://localhost:5500", "http://localhost:8099");
        });
    });
    services.AddControllers().AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.Converters.Add(new StringJsonConverter());
    });
}

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    app.UseRouting();
    app.UseCors(CORS_ALLOW_ORGINS);
    app.UseAuthorization();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

2.终结点路由+命名策略

private readonly string CORS_ALLOW_ORGINS = "cors_allow_orgins";
public void ConfigureServices(IServiceCollection services)
{
    services.AddCors(options =>
    {
        options.AddPolicy(CORS_ALLOW_ORGINS, policy =>
        {
            policy.WithOrigins("http://localhost:5500", "http://localhost:8099");
        });
    });
    services.AddControllers().AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.Converters.Add(new StringJsonConverter());
    });
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    app.UseRouting();
    app.UseCors();
    app.UseAuthorization();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllerRoute("weatherforecast", "{controller=WeatherForecast}/{action=Get}").RequireCors(CORS_ALLOW_ORGINS);
        // endpoints.MapControllers();
    });
}

3.命名策略+EnableCorsAttribute

public void ConfigureServices(IServiceCollection services)
{
    services.AddCors(options =>
    {
        options.AddPolicy("controller_cors", policy =>
        {
            policy.WithOrigins("http://localhost:5500", "http://localhost:8099");
        });
        options.AddPolicy("action_cors", policy =>
        {
            policy.WithOrigins("http://localhost:5500", "http://localhost:8099");
        });
    });
    services.AddControllers().AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.Converters.Add(new StringJsonConverter());
    });
}

// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    app.UseRouting();
    app.UseCors();
    app.UseAuthorization();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
}

然后在相关的Controller和Action上面设置EnableCorsAttribute特性。