ReadOnlyCollectionBase.ICollection.SyncRoot Property
Definition
Important
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Gets an object that can be used to synchronize access to a ReadOnlyCollectionBase object.
property System::Object ^ System::Collections::ICollection::SyncRoot { System::Object ^ get(); };object System.Collections.ICollection.SyncRoot { get; }member this.System.Collections.ICollection.SyncRoot : obj ReadOnly Property SyncRoot As Object Implements ICollection.SyncRootProperty Value
An object that can be used to synchronize access to the ReadOnlyCollectionBase object.
Implements
Examples
The following code example shows how to lock the collection using the SyncRoot property during the entire enumeration.
// Get the ICollection interface from the ReadOnlyCollectionBase
// derived class.
ICollection^ myCollection = myReadOnlyCollection;
bool lockTaken = false;
try
{
Monitor::Enter(myCollection->SyncRoot, lockTaken);
for each (Object^ item in myCollection);
{
// Insert your code here.
}
}
finally
{
if (lockTaken)
{
Monitor::Exit(myCollection->SyncRoot);
}
}
// Get the ICollection interface from the ReadOnlyCollectionBase
// derived class.
ICollection myCollection = myReadOnlyCollection;
lock(myCollection.SyncRoot)
{
foreach (object item in myCollection)
{
// Insert your code here.
}
}
' Get the ICollection interface from the ReadOnlyCollectionBase
' derived class.
Dim myCollection As ICollection = myReadOnlyCollection
SyncLock myCollection.SyncRoot
For Each item As Object In myCollection
' Insert your code here.
Next item
End SyncLock
Retrieving the value of this property is an O(1) operation.
Remarks
Derived classes can provide their own synchronized version of the ReadOnlyCollectionBase class using the SyncRoot property. The synchronizing code must perform operations on the SyncRoot property of the ReadOnlyCollectionBase object, not directly on the ReadOnlyCollectionBase object. 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 ReadOnlyCollectionBase 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.
