Action< T>当所有其他对类实例的引用被删除时，防止封闭类实例被GCed

我想知道Action<T>是否阻止了当所有其他对此类类实例的引用在运行时被删除时封闭类实例被垃圾收集?

public class Class1
{
    private Action<string> _callback;
    public Class1(Action<string> callback)
    {
        _callback = callback;
    }
    public void DoSomething(string msg)
    {
        _callback(msg);
    }
}
public class Class2
{
    private List<Class1> _class1s;
    public Class2()
    {
        _class1s = new List<Class1>();
    }
    public void AddClass1Instance()
    {
        _class1s.Add(new Class1(OnClass1DoSomething));
    }
    public void RemoveLastClass1Instance()
    {
        if(_class1s.Count > 0)
        {
            _class1s.RemoveAt(_class1s.Count - 1);
        }
    }
    private void OnClass1DoSomething(string msg)
    {
    }
}

在这个简单的例子中，当我在Class2中调用RemoveLastClass1Instance()时，Class1实例将被垃圾收集，还是通过Action<string>保留对OnClass1DoSomething()的引用?我的目标是完全删除Class1实例，并对它们进行垃圾收集。

编辑:(根据Jon Skeet的评论，我添加了以下代码以更好地理解

public class Class1
{
    public event Action<string> Event;
    public Class1()
    {
    }
    public void DoSomething(string msg)
    {
        var handle = Event;
        if (handle != null)
        {
            handle(msg);
        }
    }
}
public class Class2
{
    private List<Class1> _class1s;
    public Class2()
    {
        _class1s = new List<Class1>();
    }
    public void AddClass1Instance()
    {
        var newClass1Instance = new Class1();
        newClass1Instance.Event += OnClass1DoSomething;
        _class1s.Add(newClass1Instance);
    }
    public void RemoveLastClass1Instance()
    {
        if(_class1s.Count > 0)
        {
            _class1s.RemoveAt(_class1s.Count - 1);
        }
    }
    private void OnClass1DoSomething(string msg)
    {
    }
}