Edit in JSFiddle

var cv = new wijmo.collections.CollectionView();
cv.items.push({ name: "", value: null });
cv.items.push({ name: "Data1", value: 1 });
cv.items.push({ name: "Data2", value: 2 });
cv.items.push({ name: "Data3", value: 3 });
cv.moveCurrentToFirst();

var comboBox = new wijmo.input.ComboBox("#ComboBox", {
    itemsSource: cv,
    displayMemberPath: "name",
    selectedValuePath: "value",
    isRequired: false
});

comboBox.selectedIndexChanged.addHandler(function (s, e) {
    console.log('selectedIndex = ' + comboBox.selectedIndex);
});

<div id="ComboBox"></div>

.wj-listbox-item {
    height: 24px;
}