Not able to Checkout Component or Page after adding Event Handler

Question

I am adding event handler for CheckOutEventArgs, and am trying to get the checkout user details. Below is my code.

public void Subscribe()
{
    EventSystem.Subscribe<Page, CheckOutEventArgs>(PageCheckOutWarning,
                                                   EventPhases.Initiated);
    EventSystem.Subscribe<Component, CheckOutEventArgs>(ComponentCheckOutWarning,
                                                        EventPhases.Initiated);
} 

private void ComponentCheckOutWarning(Component component, 
                                      CheckOutEventArgs args, EventPhases phase)
{
    logdetails("Checkout User-->" + component.CheckOutUser.Title.ToString());
}

When I try to checkout the Component/Page I get this error in the Tridion Explorer error message box.

Object Reference not set to an instance of an object

Answer 1

You have subscribed to Initiated phase, in this phse item is not checked out yet, hence no CheckOutUser. You should subscribe to some of the later phases.

Also, I don't know what your code is doing, but you might consider subscribing to some generic class, like VersionedItem that contains both component and page.

Again, not knowing your idea, but take a look at SubscribeAsync method if you want to have just warning. This way it will execute faster.

If you still want to know the user in the initiated phase - you can get it from session: component.Session.User.Title

You can subscribe to VersionedItem and then in the event handler do:

private void CheckOutWarning(VersionedItem item, CheckOutEventArgs args, EventPhases phase)
{
    if (item.GetType().Name == "Component" || item.GetType().Name == "Page")
    {
    }
}

Do you want to have just warning, or do you want to prevent CheckOut?