Hello Reena,

There could be several different implementations of how to use an igCombo and its selection to populate a dataSource to be used in another igCombo. I have prepared a code sample implementing such scenatio. I have handled dropDownClosed event and based on the selection populate and bind a dataSource to be used for the second igCombo.

       var colors = [
            { Name: "Black" },
            { Name: "Blue" },
            { Name: "Brown" },
            { Name: "Green" },
            { Name: "Orange" },
            { Name: "Purple" },
            { Name: "Red" },
            { Name: "White" },
            { Name: "Yellow" },
        ];

var dsFromComboBox = [];

$(function() {

    $("#multiSelectCombo").igCombo({
        width: "270px",
        dataSource: colors,
        textKey: "Name",
        valueKey: "Name",
        multiSelection: "onWithCheckboxes",
        dropDownClosed: function(evt, ui) {

            //clear the last selection DataSource dsFromComboBox
            dsFromComboBox.length = 0;
            //clear the checkboxSelectCombo selection
            $("#checkboxSelectCombo").igCombo("selectedIndex", -1);
            var valuesToAdd = [];
            var valuesToAdd = ui.owner.values();
            var length = valuesToAdd.length;

            for (i = 0; i < length; i++) {
                var tmp = "";
                tmp = ui.owner.values()[i]
                    dsFromComboBox.push(tmp)
                    $("#checkboxSelectCombo").igCombo("dataBind");
            }
        }
    });

    $("#checkboxSelectCombo").igCombo({
        width: "270px",
        dataSource: dsFromComboBox,
        textKey: "Name",
        valueKey: "Name",
        multiSelection: "onWithCheckboxes"
    });
});

For more details please refer to the file attachment.

Just for reference, here is an online sample illustrating the use of Cascading Combos.

http://igniteui.com/combo/cascading-combos

It covers a scenario when the values populated in the next lv Combo depend on the previous lv combo selection.