所以我有一个使用Knockout绑定的许多select2下拉列表。最初它看起来工作得很好。当用户进行选择（多选）时。模型被更新，生活很好。当你有来自模型的值，你想默认显示为选中时，我的问题就来了。例如，当编辑某个东西时。你用预先填充的值加载表单。
这是我的绑定处理程序

ko.bindingHandlers.select2 = {
    init: function (el, valueAccessor, allBindingsAccessor) {
        ko.utils.domNodeDisposal.addDisposeCallback(el,
            function () {
                $(el).select2('destroy');
            });

        var allBindings = allBindingsAccessor(),
            select2 = ko.utils.unwrapObservable(allBindings.select2);

        $(el).select2(select2);
    },
    update: function (el, valueAccessor, allBindingsAccessor) {
        var allBindings = allBindingsAccessor();

        if ("value" in allBindings) {
            if ((allBindings.select2.multiple || el.multiple) && allBindings.value().constructor !== Array) {
                $(el).val(allBindings.value().split(',')).trigger('change');
            } else {
                $(el).val(allBindings.value()).trigger('change');
            }
        } else if ("selectedOptions" in allBindings) {
            var converted = [];
            var textAccessor = function (value) { return value; };
            if ("optionsText" in allBindings) {
                textAccessor = function (value) {
                    var valueAccessor = function (item) { return item; }
                    if ("optionsValue" in allBindings) {
                        valueAccessor = function (item) { return item[allBindings.optionsValue]; }
                    }
                    var items = $.grep(allBindings.options(), function (e) { return valueAccessor(e) === value });
                    if (items.length === 0 || items.length > 1) {
                        return "UNKNOWN";
                    }
                    return items[0][allBindings.optionsText];
                }
            }
            $.each(allBindings.selectedOptions(),
                function (key, value) {
                    converted.push({ id: value, text: textAccessor(value) });
                });
            $(el).select2("data", converted);
        }
        $(el).trigger("change");
    }
};

selectedoptions被绑定到一个GUID列表。这是javascript端的一个字符串列表。因为我相信Select2 select需要字符串才能设置所选的值。
我的选择如下：

<select class="form-control input-sm multi-select" data-bind="selectedOptions: BrandIds, options: Brands,  valueAllowUnset: true, optionsText:'Description', optionsValue: 'Value', select2:{ placeholder: 'Please Select...', allowClear: true, multiple:'multiple'}, css: { 'jackpot-input-error': BrandIds.error() && BrandIds.isModified() }" multiple></select>

所以我发现从服务器返回的BrandIds中的初始值被删除了。我在BrandIds的subscribe中确定了这一点。subscribe函数的参数如下所示

[
{
    "status": "deleted",
    "value": "cd1f6c04-b7ae-479e-b722-65f837e65ec2",
    "index": 0
},
{
    "status": "deleted",
    "value": "bd66ebe1-080b-4455-9094-bf0464d4adbf",
    "index": 1
}

]