button disable binding based on onchanging items in dropdownlist

[Raj Krishnamurthy]

I have a dropdown loaded with revision numbers followed by edit and print buttons.

Based on my selection in the dropdown, view displays revision details and edit button to be enabled only for latest revisions selected in the dropdown list.

As every time selecting an item in the dropdown loads the page again, disable binding does not work as intended though have declared observables

self.isEditDisabled = ko.observable(false);

self.selectedRevNumber.subscribe(function (newValue) {

                    window.app.setLocation('#/Revisions/' + newValue);

                    var itemslength = $('#ddlRevision option').length;

                    if (itemslength > 0)

                    {

                        if (ddlRevision .selectedIndex == (itemslength - 1))

                        {

                            self.isEditDisabled(false);

                            

                        }

                        else

                        {

                            self.isEditDisabled(true);

                        }

                    }

                    console.log("disable edit button " + self.isEditDisabled());

                });

Any help would be appreciated much.