How to achieve dialog with lookup control

How to create a dialog with the lookup as a control, the other control SalesId ItemId lookup is the only thing that SalesId.

Done as follows.
1.declare control by extended data type to use.

class LookupDialog extends RunBase
{
    FormStringControl   SalesIdCtrl, ItemIdCtrl;
}

2. Creation dialog.

protected Object dialog(Dialog dialog, boolean forceOnClient)
{
    DialogRunBase ret;
    ;
    ret = super(dialog, forceOnClient);
    ret.caption('Costing report by order');

    SalesIdCtrl = ret.formBuildDesign().addControl(FormControlType::String,'SalesId');
    SalesIdCtrl.extendedDataType(extendedTypeNum('SalesId'));

    ItemIdCtrl = ret.formBuildDesign().addControl(FormControlType::String,'ItemId');
    ItemIdCtrl.extendedDataType(extendedTypeNum('ItemId'));

    return ret;
}

3.Set the control can not override method at runtime.

public void dialogPostRun(DialogRunbase dialog)
{
    ;
    super(dialog);
    dialog.dialogForm().formRun().controlMethodOverload(true);
    dialog.dialogForm().formRun().controlMethodOverloadObject(this);
    SalesIdCtrl = dialog.dialogForm().formRun().design().controlName('SalesId');
    ItemIdCtrl = dialog.dialogForm().formRun().design().controlName('ItemId');
}

4.Creating lookup method.

void ItemId_lookup()
{
    Query                   query          = new Query();
    SysTableLookup          sysTableLookup =
    SysTableLookup::newParameters(tableNum(SalesLine), SalesIdCtrl);
    ;
    sysTableLookup.addLookupField(fieldNum(SalesLine, ItemId));
    sysTableLookup.addLookupField(fieldNum(SalesLine, Name));
    query.addDataSource(tableNum(SalesLine)).addRange(fieldNum(SalesLine,SalesId)).value(SalesIdCtrl.text());
    sysTableLookup.parmQuery(query);
    sysTableLookup.performFormLookup();
}

5.Detailed method other

public container pack()
{
    return conNull();
}

public boolean unpack(container packedClass)
{
    return true;
}

static void main(Args _args)
{
    LookupDialog test1 = new LookupDialog();
    ;
    if (test1.prompt())
    {
        test1.run();
    }
}