https://www.cnblogs.com/ianunspace/p/5508179.html
//解决方法：
//引入命名空间：
using System.Security.Cryptography.X509Certificates;
using System.Net.Security;
//定义方法：
private static bool RemoteCertificateValidate(object sender, X509Certificate cert, X509Chain chain, SslPolicyErrors error)
{
//为了通过证书验证，总是返回true
return true;
}
//调用方法一：
//在构造函数中调用：
static WxRequest()
{
// 获取验证证书的回调函数
ServicePointManager.ServerCertificateValidationCallback+=RemoteCertificateValidate;
}
//方法二：
//在WebRequest请求之前调用：
ServicePointManager.ServerCertificateValidationCallback+=RemoteCertificateValidate;