Public Overridable ReadOnly Property SyncRoot As Object

Dim instance As ArrayList
Dim value As Object

value = instance.SyncRoot

public virtual Object SyncRoot { get; }

public:
virtual property Object^ SyncRoot {
    Object^ get ();
}

public function get SyncRoot () : Object

Implements

To create a synchronized version of the ArrayList, use the Synchronized method. However, derived classes can provide their own synchronized version of the ArrayList using the SyncRoot property. The synchronizing code must perform operations on the SyncRoot of the ArrayList, not directly on the ArrayList. This ensures proper operation of collections that are derived from other objects. Specifically, it maintains proper synchronization with other threads that might be simultaneously modifying the ArrayList object.

Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

The following code example shows how to lock the collection using the SyncRoot during the entire enumeration.

ArrayList myCollection = new ArrayList();
  lock(myCollection.SyncRoot) {
  foreach (Object item in myCollection) {
  // Insert your code here.
  }
 }

Dim myCollection As New ArrayList()
 Dim item As Object
 SyncLock myCollection.SyncRoot
  For Each item In myCollection
  ' Insert your code here.
  Next item
 End SyncLock

Retrieving the value of this property is an O(1) operation.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

.NET Framework

.NET Compact Framework

XNA Framework

Reference