ASP.NET CORE 3.1 跨域中间件

using Microsoft.AspNetCore.Http;
using System.Threading.Tasks;

namespace Core.Api
{
    /// <summary>
    /// 跨域中间件
    /// </summary>
    public class CorsMiddleware
    {
        private readonly RequestDelegate _next;

        /// <summary>
        /// 管道执行到该中间件时候下一个中间件的RequestDelegate请求委托，如果有其它参数，也同样通过注入的方式获得
        /// </summary>
        /// <param name="next">下一个处理者</param>
        public CorsMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        /// <summary>
        /// 自定义中间件要执行的逻辑
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        public async Task Invoke(HttpContext context)
        {
            context.Response.Headers.Add("Access-Control-Allow-Origin", "*");
            context.Response.Headers.Add("Access-Control-Allow-Headers", context.Request.Headers["Access-Control-Request-Headers"]);
            context.Response.Headers.Add("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS");

            //若为OPTIONS跨域请求则直接返回,不进入后续管道
            if (context.Request.Method.ToUpper() != "OPTIONS")
                await _next(context);//把context传进去执行下一个中间件
        }
    }
}

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    app.UseMiddleware<CorsMiddleware>()//跨域
}

 利用ajax跨域请求调用：需要加头部请求

headers: {
　　'Content-Type': 'application/json;charset=utf-8'
}

后台是类对象：

ajax向后台传递参数为对象实例：

data: JSON.stringify({
        'username': name,
        'password': pwd
    }),

<script>
    function btntest() {
        $.ajax({
            type: 'post',
            url: 'http://localhost:5000/Base_Manage/Home/SubmitLogin',
            dataType: 'json',
            data: JSON.stringify({
                'userName':'admin',
                'password': '123456'
            }),
            contentType: false,
            headers: {
                'Authorization': '',
                'Content-Type': 'application/json;charset=utf-8'
               
            },
            success: function (res) {
                
                console.log(res);
            },
            error: function (err) {
                reject(err)
            }
        });
    }
</script>