multi-threading with abstract protected member?

Question

I'm considering an existing multi-threading C# application and noticed some code like

public abstract class Task
{
    protected IList<string> action;

...

    public void Initialize (params)
    ...

Several special "Tasks" derive from Task and some Task methods modify "action". So in my idea, this is not thread safe. Am I right ?

Thanks for any help,

Olivier

Answer 1

No, you are not right. action is an instance field, so each instance of the Task-derived class will have its own copy of action. It would potentially be a problem only if action were static.

To clarify, you can have many Task-derived objects. Each one of those will work just fine for a single thread. However, you do not want to have multiple threads accessing the same Task instance, unless the code that modifies action is protected with some kind of synchronization.