Updating a custom user control in an update panel, from a control outside the update panel

I have a an update panel. Inside this is a dropdown list and a custom chart control. When the index changes, the chart control updates itself with new data and displays it. There is another c开发者_如何转开发ontrol which can affect this charts. However, as this other control is outside of the charts update panel, the chart isn't updated with the changes. Not until the dropdown even fires again and the chart is updated.

My question is, how can I get this separate control to update the chart. Do I need to somehow fire the update panel? I'm lost with this?

Thanks in advance

Two options:

1. Set the updatePanel's UpdateModel to Conditional and call it`s Update Method from codebehind
2. Define an AsyncPostbackTrigger on the aspx-markup of the UpdatePanel for the control outside of the UpdatePanel