by Andreas

KnockoutJS – how to force binding refresh / re-evaluation

Observable bindings in KnockoutJS get re-evaluated when the focus is changed in a form, for instance when you click a button or use TAB to move from one input field to the next. When KnockoutJS is used in combination with an ASP.NET panel control where a DefaultButton is defined, re-evaluation of observable bindings is not performed when the user clicks ENTER to trigger the button click event. As a result of this, a value entered in an input field that is bound to the view model will not be registered if the user doesn’t navigate (move focus) away from the field first. 

A work-around for this is to use jQuery (or pure javascript) and programmatically set the focus to a different control, for instance the button itself when the event is fired.

self.addNewTimeRegEntry = function () {
    // set focus to button control to force re-evaluation
    $("#<%= btnAddRegEntry.ClientID %>").focus();

    ... // continue as normal

The button click event is bound to the addNewTimeRegEntry function above (through the KnockoutJS framework), and by moving the focus all variables will be refreshed before further processing is done.