Problems with events

[Dirk]

Hello,

I have a class library with many classes and properties. For every
property I have a PropertyNameChanged event. In my user interface layer
it sometimes happens that I subscribe such an event from multiple
places.

For example, I have a Property "Active" on a class. This property is
bounded to a CheckBox control in a user control. When this property
changes to false, there is one code which removes the UserControl from
the form (in some circumstances). The DataBinding code of the CheckBox
also subscribes my ActiveChanged event to refresh the control.

My problem is that when I trigger the ActiveChaged event in my class
library, I get a NullReference exception in the
System.Windows.Forms.BindToObject.PropValueChanged method. I
reflectored that method: The reason is that the bindingManager object
is null, and I understand why: When I trigger the event in the class
library, I do not care and I dont want to care about the order in which
the several event handler methods are fired. So in my case, the handler
which removes my usercontrol fires first. at that moment, the
databinding is removed. But the second event handler (PropValueChanged
in the BindToObject class) is still fired.

To find a workarraund to this problem is not to difficult, I could
remove the databindung from that checkbox. But I´m sure I will have
that problem on multiple places and I would like to know a correct
solution. So where is my failure?

best regards

Dirk