Overriding ToString() of List<MyClass>

I have a class MyClass, and I would like to override the method ToString() of instances of List:

class MyClass
{
    public string Property1 { get; set; }
    public int Property2 { get; set; }
    /* ... */
    public override string ToString()
    {
        return Property1.ToString() + "-" + Property2.ToString();
    }
}

I would like to have the following:

var list = new List<MyClass>
            {
                new MyClass { Property1 = "A", Property2 = 1 },
                new MyClass { Property1 = "Z", Property2 = 2 },
            };

Console.WriteLine(list.ToString());   /* prints: A-1,Z-2 */

Is it possible to do so? Or I would have to subclass List<MyClass> to override the method ToString() in my subclass? Can I solve this problem using extension methods (ie, is it possible to override a method with an extension method)?

Thanks!