ComboBox is not a constructor

define(["dojo/store/Memory","dojo/_base/declare","md/myownclass","dijit/form/ComboBox", "dojo/query", "dojo/keys", "dijit/Tooltip", "dojo/on","dojo/dom","dojo/dom-construct"],
function(Memory,declare, myownclass, ComboBox, query, keys, Tooltip, on, dom, domConstruct){
    return declare(null,{
        MyMemory : null,
        comboBox : null,
        //keyhandle : null,
        //oldval : "",
        constructor: function(){
            this.MyMemory = new myownclass();
            var stateStore = new Memory({data : this.MyMemory.data});
            comboBox = new ComboBox({
                            id: "stateSelect",
                            name: "state",
                            value: "",
                            store: stateStore,
                        searchAttr: "name"
                        }, "stateSelect");
                handle = on(dom.byId("stateSelect"),"keyup", this.keyupfoo);
            },
    keyupfoo : function(pressed)
        {
            if(pressed.keyCode == keys.ENTER){
                var value = dijit.byId('stateSelect').get('value');
                var isNew = true;
                var d = MyMemory.getdata();
                for(var index = 0; index < d.length ; index++)
                {
                    if(value == d[index])
                    {
                        isNew = false;
                    }
                }
                if(isNew == true){
                    MyMemory.setdata(value);
                }
            }
            if(pressed.keyCode == keys.NUMPAD_MINUS && pressed.keyCode.ctrlKey == true){
                    MyMemory.deletedata(value);
            }
            if(pressed.keyCode == keys.NUMPAD_MULTIPLY && pressed.keyCode.ctrlKey == true){
                if(oldval == ""){
                    oldval = value;
                }
                else{
                    MyMemory.updatedata(value,oldval);
                    oldval = "";
                }
            }
            if(pressed.keyCode == keys.F1){
                new Tooltip({
                    connectId: ["stateSelect"],
                    label: "CTRL+'-' will delete existing entry <br> Updating existing Entry please mark an Entry press CTRL+'*' and write a new Entry and repress CTRL+'*'!"
                });
            }
        }

    });
});