Change Password in DotnetNuke using UserId

UserController objCont = new UserController();
UserInfo obInfo = new UserInfo();

//Get information of of User by userID
obInfo = objCont.GetUser(PortalId, USERID);

//Use of Membership to get user deatil by username after getting information
MembershipUser objUser1 = Membership.GetUser(obInfo.Username);

string strOdPassword = objUser1.GetPassword();// give old password
objUser1.ChangePassword(strOdPassword, “New password String”);