asp.net core 3 跨域

当出现

The CORS protocol does not allow specifying a wildcard (any) origin and credentials at the same time. Configure the CORS policy by listing individual origins if credentials needs to be supported 跨域错误的时候

只需要给予一个可信列表即可。修改内容如下：

        services.AddCors(options => options.AddPolicy("CorsPolicy",
            builder =>
            {
                builder.WithOrigins(new string[] { "http://127.0.0.1:5500" })
                    .AllowAnyMethod()
                    .AllowAnyHeader()
                    .AllowCredentials();
            }));

如果真的就不想做任何限制，其实也是有办法的。只需要将AllowAnyOrigin替换为SetIsOriginAllowed(_ => true)就可以解决。

   services.AddCors(options => options.AddPolicy("CorsPolicy",
            builder =>
            {
                builder.AllowAnyMethod()
                    .SetIsOriginAllowed(_ => true)
                    .AllowAnyHeader()
                    .AllowCredentials();
            }));

除了前面的两个方法以外，其实还可以自定义中间件。添加Cors处理类。如下：

    public class CorsMiddleware
    {
        private readonly RequestDelegate next;

        public CorsMiddleware(RequestDelegate next)
        {
            this.next = next;
        }
        public async Task Invoke(HttpContext context)
        {
            if (context.Request.Headers.ContainsKey(CorsConstants.Origin))
            {
                context.Response.Headers.Add("Access-Control-Allow-Origin", context.Request.Headers["Origin"]);
                context.Response.Headers.Add("Access-Control-Allow-Methods", "PUT,POST,GET,DELETE,OPTIONS,HEAD,PATCH");
                context.Response.Headers.Add("Access-Control-Allow-Headers", context.Request.Headers["Access-Control-Request-Headers"]);
                context.Response.Headers.Add("Access-Control-Allow-Credentials", "true");

                if (context.Request.Method.Equals("OPTIONS"))
                {
                    context.Response.StatusCode = StatusCodes.Status200OK;
                    return;
                }
            }

            await next(context);
        }
    }

在Configure方法中添加如下内容即可。

app.UseMiddleware<CorsMiddleware>();