Just to comment first, please make sure any source code is neatly formatted when you ask a question. Unless people can read it they probably won't help you. It's an absolute nightmare trying to read that, but as your question/problem is a good one I'll answer anyway...
Here's a working example based on your code. The key bits are in bold...
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
AccordionItem RSR = new AccordionItem();
RSR.Header = "RSR";
AccordionItem Supervisors = new AccordionItem();
Supervisors.Header = "Supervisors";
AccordionItem Managers = new AccordionItem();
Managers.Header = "Managers";
ContextMenu RSRContext = new ContextMenu();
ContextMenu SupervisorsContext = new ContextMenu();
ContextMenu ManagersContext = new ContextMenu();
MenuItem jeff = new MenuItem { Header = "Jeff" };
jeff.Click += new RoutedEventHandler(MenuSelected_Click);
MenuItem bob = new MenuItem { Header = "Bob" };
bob.Click += new RoutedEventHandler(MenuSelected_Click);
RSRContext.Items.Add(jeff);
RSRContext.Items.Add(bob);
MenuItem sheenagh = new MenuItem { Header = "Sheenagh" };
sheenagh.Click += new RoutedEventHandler(MenuSelected_Click);
MenuItem mike = new MenuItem { Header = "Mike" };
mike.Click += new RoutedEventHandler(MenuSelected_Click);
SupervisorsContext.Items.Add(sheenagh);
SupervisorsContext.Items.Add(mike);
MenuItem alice = new MenuItem { Header = "Alice" };
alice.Click += new RoutedEventHandler(MenuSelected_Click);
MenuItem luke = new MenuItem { Header = "Luke" };
luke.Click += new RoutedEventHandler(MenuSelected_Click);
ManagersContext.Items.Add(alice);
ManagersContext.Items.Add(luke);
RSR.Content = RSRContext;
Supervisors.Content = SupervisorsContext;
Managers.Content = ManagersContext;
accordion1.Items.Add(RSR);
accordion1.Items.Add(Supervisors);
accordion1.Items.Add(Managers);
accordion1.SelectionMode = AccordionSelectionMode.ZeroOrOne;
}
void MenuSelected_Click(object sender, RoutedEventArgs e)
{
MenuItem item = sender as MenuItem;
MessageBox.Show("You clicked on: " + item.Header.ToString());
}
PS Please mark as the answer if this helps.