how to multiple checkbox use in combobox windows application C#

I am building a windows store app.

I have to implement checkbox inside combobox. I am stucked at following problem:I want to display the checked Item in "Combobox with Checkbox"

private void comboBox4_DropDown(object sender, EventArgs e)
{
    checkedListBox1.Visible = true;
}

private void comboBox4_DropDownClosed(object sender, EventArgs e)
{
    checkedListBox1.Visible = false;
}