How can you add a Certificate to WebClient (C#)?

Solution 1:

You must subclass and override one or more functions.

class MyWebClient : WebClient
{
    protected override WebRequest GetWebRequest(Uri address)
    {
        HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
        request.ClientCertificates.Add(new X509Certificate());
        return request;
    }
}

Solution 2:

public class CertificateWebClient : WebClient
{
    private readonly X509Certificate2 certificate;

    public CertificateWebClient(X509Certificate2 cert)
    {
        certificate = cert;
    }

    protected override WebRequest GetWebRequest(Uri address)
    {
        HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);

        System.Net.ServicePointManager.ServerCertificateValidationCallback = delegate(Object obj, X509Certificate X509certificate, X509Chain chain, System.Net.Security.SslPolicyErrors errors)
        {
            return true;
        };

        request.ClientCertificates.Add(certificate);
        return request;
    }
}

Now you can with self signed cert ! ("The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.; The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.;")

        X509Certificate2 Cert = new X509Certificate2("client.p12", "1234", X509KeyStorageFlags.MachineKeySet);

        // Create a new WebClient instance.
        CertificateWebClient myWebClient = new CertificateWebClient(Cert);

        string fileName = Installation.destXML;
        string uriString = "https://xxxxxxx.xx:918";
        // Upload the file to the URI.
        // The 'UploadFile(uriString,fileName)' method implicitly uses HTTP POST method.
        byte[] responseArray = myWebClient.UploadFile(uriString, fileName);

        // Decode and display the response.
        Console.WriteLine("\nResponse Received.The contents of the file uploaded are:\n{0}",
            System.Text.Encoding.ASCII.GetString(responseArray));