ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

ClientCredentials credentials = new ClientCredentials();
credentials.UserName.UserName = "************";
credentials.UserName.Password = "*******";
Uri serviceUri = new Uri("");
OrganizationServiceProxy proxy = new OrganizationServiceProxy(serviceUri, null, credentials, null);
proxy.EnableProxyTypes();
var _service = (IOrganizationService)proxy;