What are the steps to tracking down a bug?
What is your system?
Well I like to first look at what I am trying to achieve:
Add/Delete data from the map and having the changes appear at another client automatically.
What is the current change?
Deleting data automatically affects other clients.
The bug:
When deleting Boo entities all other Boo entities on the screen get deleted.
Tracking down the code that is probably responsible:
private void AreDeletedTask_ExecuteCompleted(object sender, QueryEventArgs e)
{
var toDelete = new List<Graphic>();
foreach (var graphic in Graphics)
{
var id = GetObjectId(graphic);
if ((e.FeatureSet.ObjectIDs == null || !e.FeatureSet.ObjectIDs.Contains(id)) &&
graphic.Geometry.Extent.Intersects(_map.Extent))
toDelete.Add(graphic);
}
foreach (var graphic in toDelete)
{
Graphics.Remove(graphic);
}
}
Just from looking at the code I can tell that the toDelete list must contain all the graphic elements in the extent.
So what do we have here? This is the result of a task that queries elements missing from an update to the current extent.
Let say I have a,b,c,d Boo elements.
a,b – were deleted
c – was unchanged
d – was updated
Only b,c,d are in the extent.
The query will be on the existence of a,b,c.
The result given to this method should contain only c element.
toDelete should contain b only.
But what about the case:
a – was deleted
b,c,d – were unchanged
The query will be on the existence of a, and will return null.
Now toDelete will contain a,b,c,d – Found The Bug!
