Assembly: WindowsBase (in windowsbase.dll)
If there was a call to BlockReentrancy of which the IDisposable return value has not yet been disposed of. Typically, this means when there are additional attempts to change this collection during a CollectionChanged event. However, it depends on when derived classes choose to call BlockReentrancy.
Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter EditionThe Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.