C#调用webapi HTTPS报错：基础连接已经关闭: 未能为 SSL/TLS 安全通道建立信任关系--安全证书问题

1、首先加入命名空间：
using System.Net.Security;
using System.Security.Authentication;
using System.Security.Cryptography.X509Certificates;

SSL网站，连接时需要提供证书，对于非必须提供客户端证书的情况，只要返回一个安全确认即可。我的是.NET FrameWork4.0

2、加入以下代码：

publicboolCheckValidationResult(object sender,X509Certificate certificate,X509Chain chain,SslPolicyErrors errors){//直接确认，否则打不开returntrue;}

3、接收证书进行身份验证ssl,在调用api接口前调用此方法：

 ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(CheckValidationResult);

以下是完整案例：

publicstringHttpPost(string url,string body){Encoding encoding = Encoding.UTF8;string jsonText =string.Empty;string dataText1 =string.Empty;if(string.IsNullOrEmpty(url.Trim())){return"";}//接收证书进行身份验证
        ServicePointManager.ServerCertificateValidationCallback =newSystem.Net.Security.RemoteCertificateValidationCallback(CheckValidationResult);//ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;HttpWebRequest request =(HttpWebRequest)WebRequest.Create(url);
        request.Method ="POST";
        request.Accept ="text/plain, */*; q=0.01";
        request.ContentType ="application/json;charset=utf-8";byte[] buffer = encoding.GetBytes(body);
        request.ContentLength = buffer.Length;
        request.GetRequestStream().Write(buffer,0, buffer.Length);HttpWebResponse response =(HttpWebResponse)request.GetResponse();using(StreamReader reader =newStreamReader(response.GetResponseStream(), Encoding.UTF8)){
            jsonText = reader.ReadToEnd();
            dataText1 = Regex.Replace(jsonText,@"\\","");}return dataText1;}

调用：

dlbzUrl是调用地址 https://…/api/tddbzzljcxt/zybrxx/vnoentry-query
model.FCYRQSTART 开始时间
model.FCYRQEND 结束时间

string DaliBaiHospitalJson =HttpPost(dlbzUrl,"{\"FIDATES\":\""+ model.FCYRQSTART +" 00:00:00"+"\",\"FIDATEE\":\""+ model.FCYRQEND +" 23:59:59"+"\"}");