/// <summary>
/// 第三方子网站通过这个方法拿到当前的code
/// </summary>
/// <param name="appid"></param>
/// <param name="returnUrl"></param>
public static void GetCode(string appid)
{
JsApiPay jsApiPay = new JsApiPay(System.Web.HttpContext.Current);
jsApiPay.GetCodeByAppId(appid);
}