<script type="text/javascript">
        var initparam = "/UsersApi/api/Ats/GetUserList"

        function initList(queryurl) {
            $.getJSON(queryurl, function (allData) {
                viewModel.UserList = ko.mapping.fromJS(allData, {}, viewModel.UserList);
            });
        }

        var UsersViewModel = function (initparam) {
            var self = this;
            var init = [
            { serial: 0, familyname: "AllUsers"}];
            self.UserList = ko.observableArray([]);
            initList(initparam);
        }

        var viewModel = new UsersViewModel(initparam)
        ko.applyBindings(viewModel);
    </script>

<select id="listGetUserBySer" 
class="form-control" 
data-bind="options: UserList, optionsText: 'familyname', optionsValue: 'serial'">
</select>