[Mono-bugs] [Bug 81771][Wis] New - Null object reference after ListControl.DataSource is set to null

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Changed by albright at wesay.org.

http://bugzilla.ximian.com/show_bug.cgi?id=81771

--- shadow/81771	2007-05-29 03:30:53.000000000 -0400
+++ shadow/81771.tmp.7898	2007-05-29 03:30:53.000000000 -0400
@@ -0,0 +1,43 @@
+Bug#: 81771
+Product: Mono: Class Libraries
+Version: 1.2
+OS: 
+OS Details: 
+Status: NEW   
+Resolution: 
+Severity: 
+Priority: Wishlist
+Component: Windows.Forms
+AssignedTo: toshok at ximian.com                            
+ReportedBy: albright at wesay.org               
+QAContact: mono-bugs at ximian.com
+TargetMilestone: ---
+URL: 
+Cc: 
+Summary: Null object reference after ListControl.DataSource is set to null
+
+Please fill in this template when reporting a bug, unless you know what you
+are doing.
+Description of Problem:
+When a ListControl has a DataSource assigned to it, it registers
+OnPositionChanged with that DataSource, however when null is assigned to
+the DataSource, it does not unregister OnPositionChanged so that when the
+position changes, data_manager is null and you get an exception: Object
+reference not set to an instance of an object.
+
+Steps to reproduce the problem:
+1. Assign a List into a ListControl.DataSource
+2. Assign null into a ListControl.DataSource
+3. Change the content of the List (Add a new item to the beginning of the
+list for example)
+
+Actual Results:
+crash
+
+Expected Results:
+no crash
+
+How often does this happen? 
+Always
+
+Additional Information: