Typically the enumerator does not have exclusive access to the collection; therefore, enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads could still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can follow one of the following strategies:

• Lock the collection during the entire enumeration using a System.Threading.Monitor.

• Catch and handle the exceptions that result from changes made by other threads.

Namespace: System.Windows.Forms.Layout
Assembly: System.Windows.Forms (in System.Windows.Forms.dll)
Assembly Versions: 2.0.0.0
Since: .NET 2.0