c# 跨域api

前端 ajax get请求

 $.ajax({
            url: "API地址",
            type: 'get',
            dataType: 'jsonp',
            async: true,
            processData: true,
            contentType: false,

            success: function (res) {
                console.log(res)
            },
            error: function (Error) {
                console.log(Error)
            }
        })

前端 ajax post请求

$.ajax({
            type: 'post',
            url: 'API地址',
            data: data,
            dataType: "json",
            crossDomain: true,
            success: function (data) {
                console.log(data);

            },
            error: function (data) {
                console.log(data);

            }
        });

c# 后端 get请求

var res="最好转换成json";
string callback = this.Request["callback"];
return Content(callback + "(" + res + ")");

c# 后端 post 请求

//1.可以创建一个FilterAttribute
public class PostAPIController : ActionFilterAttribute
    {
　　　　　//override  OnActionExecuting
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            //设置
            filterContext.HttpContext.Response.Headers.Add("Access-Control-Allow-Origin", "*");
            filterContext.HttpContext.Response.Headers.Add("Access-Control-Allow-Methods", "POST");
            filterContext.HttpContext.Response.Headers.Add("Access-Control-Allow-Headers", "x-requested-with,content-type");

            base.OnActionExecuting(filterContext);
        }
    }

　　　　//2.post请求代码块   加上过滤器 PostAPIController
　　　　
        [HttpPost]
        [PostAPIController]
        public ActionResult AddReadNum(int newid)
        {
            try
            {
                *******
　　　　　　　　　 *******
if (string.IsNullOrEmpty(callback))
                {
                    return Json(result, JsonRequestBehavior.AllowGet);
                }
                else
                {
                    string res = JsonToots.ModelToJson(result);
                    return Content(callback + "(" + res + ")");

                }

            }
            catch (Exception ex)
            {
                ******
            }
        }