| Steps To Reproduce | The implementation of EventTrigger's RegisterEvent method, as follows
[code]
private void RegisterEvent(object source, string eventName)
{
if (source != null && !string.IsNullOrEmpty(eventName))
{
Type type = source.GetType();
EventInfo ev = type.GetEvent(eventName);
if (ev == null)
{
if (SourceObject != null)
{
throw new ArgumentException(string.Format(
"EventTrigger cannot find event '{0}' in SourceObject '{1}'",
eventName, type));
}
}
if (!IsValidEvent(ev))
{
if (SourceObject != null)
{
throw new ArgumentException(string.Format(
"SourceObject event '{0}' is not valid for EventTrigger",
eventName));
}
}
else
{
_event = ev;
_handler = Delegate.CreateDelegate(ev.EventHandlerType, this, OnEventMethod);
_event.AddEventHandler(source, _handler);
}
}
}
[/code]
doesn't properly handle the case where the default target object (usually AssociatedObject) exists but the designated event does not while no SourceObject is set (and thus SourceObject == null). As described above, this code will fall through with a null ev and null SourceObject and pass IsValidEvent null, which fails with a nullreferenceexception. An additional branch should be added to the condition to provide an informative message in this case. |
|---|
