c# - calling SmartObjects method in C#

Question

I created a SmartObject in K2 designer and I added the WCF url as service reference.

Below is the code

UserDetailsSvcClient userDetail = new UserDetailsSvcClient();
userDetail.Open();
UserDetails userDC = new UserDetails();
var userDetailsList = userDetail.UserDetailsSvc_Load(userDC);
userDetail.Close();

But the userDetailsList always remains as null.

Also the GetList Smart method is not appearing