Managed CSOM on Sharepoint 201. Could not create SSL/TLS secure channel - ssl

Question

I have a Windows Server 2016 VM and Visual Studio 2017 Community Edition. I am writing a simple script just to check the connectivity with the Sharepoint 2013. The Sharepoint Server is NOT installed on the VM, it is somewhere within the intranet.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.SharePoint.Client;
using System.Security;
namespace ConsoleApp1
{
class Program
{
static void Main(string[] args)
{
string siteUrl = "https://xxx.yyy.org:443";
ClientContext clientContext = new ClientContext(siteUrl);
Web site = clientContext.Web;
List documents = site.Lists.GetByTitle("Documents");
//Prepare the request
clientContext.Load(site);
//Submit the Request
clientContext.ExecuteQuery();
Console.ReadKey();
}
}
}
But I am getting this exception:
System.Net.WebException occurred
HResult=0x80131509
Message=The request was aborted: Could not create SSL/TLS secure channel.
Source=System
StackTrace:
at System.Net.HttpWebRequest.GetResponse()
at Microsoft.SharePoint.Client.SPWebRequestExecutor.Execute()
at Microsoft.SharePoint.Client.ClientContext.GetFormDigestInfoPrivate()
at Microsoft.SharePoint.Client.ClientContext.EnsureFormDigest()
at Microsoft.SharePoint.Client.ClientContext.ExecuteQuery()
at ConsoleApp1.Program.Main(String[] args) in C:\Users\AdminDD\source\repos\ConsoleApp1\ConsoleApp1\Program.cs:line
I've read this thread and I signed in through IE. The certificate of the browser seems valid and the problem remains. Is there any suggestion on how to solve this ?

Answer 1

I had the exact same issue.
Check your project .Net Version. It worked after upgrading from 4.5 --> 4.6

Answer 2

you should do a request on your url https://yoursite/ absolute url only, nothing more
$response = Invoke-WebRequest -Verbose -URI $anUrl -CertificateThumbprint $CertificateThumbprint -UseDefaultCredentials -SessionVariable websession -ErrorAction:Stop
get cookie authentification in reponse, and then add it in your csom query
$request.ClientCertificates.Add($global:cert)
$request.CookieContainer = New-Object System.Net.CookieContainer
$c3 = New-Object System.Net.Cookie($global:cookieName3, $global:cookieVal3, "/", $global:cookieDomaine);
$request.CookieContainer.Add($c3);
here is a working sample