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In C#, when you have a method that works on a List<T> (or any collection), and another part of your code triggers an event that wants to delete an object from the same list, the behavior depends on the specific context and how you've implemented your code.

Synchronization: By default, C# collections like List<T> are not thread-safe. If multiple threads are accessing and modifying the list concurrently, it can lead to issues like race conditions, exceptions, or unexpected behavior.

Blocking: If one part of your code is iterating through the list or performing an operation on it, and another part tries to delete an object from the list, it can potentially block until the first operation completes. This is because the list's internal data structure may not allow simultaneous modification and enumeration.

Concurrent Collections: If you need to work with collections in a multithreaded environment, you should consider using thread-safe collections from the System.Collections.Concurrent namespace, such as ConcurrentBag<T>, ConcurrentQueue<T>, or ConcurrentDictionary<TKey, TValue>. These collections are designed to allow safe concurrent access and modification.

Locking: Alternatively, you can use explicit locking mechanisms (e.g., lock keyword) to synchronize access to the list. This way, you can ensure that only one part of your code accesses the list at a time. However, this approach may introduce potential performance bottlenecks if used excessively.

Here's an example of using locking to synchronize access to a list:

csharpCopy code
private List<YourObject> yourList = new List<YourObject>();
private object listLock = new object();

public void SomeMethod()
{
lock (listLock)
{
// Perform operations on yourList
// ...
}
}

public void EventHandler()
{
lock (listLock)
{
// Delete an object from yourList
// ...
}
}

In summary, the behavior depends on how your code is structured and whether you've taken precautions to handle concurrent access to the list. If you anticipate multiple threads accessing and modifying the same list, consider using thread-safe collections or synchronization mechanisms to ensure consistent and safe behavior.