Error: C# The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel

Question

I\'m trying to make a request via SSL. The certificate is already installed on the machine and it works via browser.

I am using this request:

System.Text         


        

Answer 1

This is client code, right? And you're accessing an HTTPS url, aren't you? I think the problem is with the server certificate, which the client-side TLS stack cannot validate. When you connect to that URL via browser, does it work smoothly or do you see a warning on certificate mismatch?

Answer 2

Make sure your certificate is properly trusted. Has the root certificate been added to the correct certificate store (Trusted Root CA's on Local Machine)?

I encountered this error when the (own made) root certificate for a (self signed) certificate had been added to the Trusted Root CA's for Current User). Moving the root cert to the Root CA store on Local Machine solved my issue.

Answer 3

I solved the problem with this:

ServicePointManager.ServerCertificateValidationCallback = new        
RemoteCertificateValidationCallback
(
   delegate { return true; }
);