title: C# Datagridview Checkbox Checked Event - multiple rows?
body: <p>I have a datagridview with multiple columns and rows.
  The first column contains a checkbox.
  I want the user to be able to select multiple checkboxes and then perform an action.
  For example if they select checkboxes in rows 1 and 2, the data from other columns in rows 1 and 2 can be selected and passed into a messagebox.</p>
  
  <p>I know i need to use the checkbox_changed event to do this. However I am having trouble working out how to do this for multiple rows?</p>