Question

我目前正在开发ASP Net Core API，当我尝试向服务器发送PUT请求时，出现返回错误：

对预检请求的响应未通过访问控制检查：所请求的资源上没有“ Access-Control-Allow-Origin”标头

我已经准备好设置app.EnableCors（）和services.EnableCors（）了，但是即使在那之后，我仍然收到错误消息。

代码如下：

public class CorsMiddleware
{
    private readonly RequestDelegate _next;

    public CorsMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task Invoke(HttpContext context)
    {
        context.Response.Headers.Add("Access-Control-Allow-Origin", "*");
        context.Response.Headers.Add("Access-Control-Allow-Credentials", "true");
        context.Response.Headers.Add("Access-Control-Allow-Headers", "Content-Type, X-CSRF-Token, X-Requested-With, Accept, Accept-Version, Accept-Encoding, Content-Length, Content-MD5, Date, X-Api-Version, X-File-Name");
        context.Response.Headers.Add("Access-Control-Allow-Methods", "POST,GET,PUT,PATCH,DELETE,OPTIONS");
        if (context.Request.Method == "OPTIONS")
        {
            context.Response.StatusCode = (int)HttpStatusCode.OK;
            await context.Response.WriteAsync(string.Empty);
        }

        await _next(context);
    }
}

// Extension method used to add the middleware to the HTTP request pipeline.
public static class CorsMiddlewareExtensions
{
    public static IApplicationBuilder UseCorsMiddleware(this IApplicationBuilder builder)
    {
        return builder.UseMiddleware<CorsMiddleware>();
    }
}

Startup.cs看起来像这样：

public void ConfigureServices(IServiceCollection services)
{
     services.AddCors();
     services.AddMvc(ConfigureMvcOptions);
     services.AddSwaggerGen(ConfigureSwaggerOptions);
}

 public void Configure(IApplicationBuilder app, IHostingEnvironment env)
 {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        // Enable middleware to serve generated Swagger as a JSON endpoint.
        app.UseSwagger();

        app.UseMiddleware(typeof(CorsMiddleware));
        app.UseAuthentication();
        app.UseMvc();
 }

Answer 1

2天前，我遇到了这个确切的问题。我的解决方案是在需要时使管道短路。我不知道其他中间件会发生什么，但是设置状态码后，其他一些东西会改变状态码。对于选项预检请求，实际上您可能不需要执行任何其他操作。

更改此：

    if (context.Request.Method == "OPTIONS")
    {
        context.Response.StatusCode = (int)HttpStatusCode.OK;
        await context.Response.WriteAsync(string.Empty);
    }

    await _next(context);

对此：

    if (context.Request.Method == "OPTIONS")
    {
        context.Response.StatusCode = (int)HttpStatusCode.OK;
        await context.Response.WriteAsync(string.Empty);
    }
    else
    {
        await _next(context);
    }

Answer 2

转到您的Startup.cs文件

在ConfigureServices方法中添加；

services.AddCors(options =>
{
    options.AddPolicy("AllowLocalhost",
    builder => builder
    .AllowAnyOrigin()
    .AllowAnyHeader()
    .AllowAnyMethod()
    .AllowCredentials()
    .SetPreflightMaxAge(TimeSpan.FromDays(5)));
});

然后在Configure方法中添加；

app.UseCors("AllowLocalhost");

放置请求期间的ASP Net Core CORS错误

2 个答案: