custom control dropdownlist autopostback event not firing

Question

Hi

I have a custom control which encapsulates a dropdownlist and label.
when you select an item from the dropdownlist it should autopostback
and change the lable text. But postback (selectionchanged) event is
not working at all.
Here is my code.

protected override void RenderContents(HtmlTextWriter output)
        {
            this.buildControl(output);
        }

private void buildControl(HtmlTextWriter output)
        {
            Table currencyConverterTable = new Table();
            // add a label

           // here I am adding a dropdownlist
            dropdownlist currencySelector= new dropdownlist();
            currencySelector.DataSource = mydatasource;
            currencySelector.DataTextField = "CurrencyCode";
            currencySelector.DataValueField = "id";
            currencySelector.DataBind();
            currencySelector.AutoPostBack = true;
            currencySelector.SelectedIndexChanged += new
EventHandler(OnSelectedChanged);

            // add this dropdownlist to the table

           // now render it
            currencyConverterTable.RenderControl(output);
        }

Shouldn't OnSelectedChanged event be fired?

Thanks,

Toby