Is ReadOnlyCollection threadsafe if the underlying collection is not touched?

Question

MSDN vaguely mentions:

A ReadOnlyCollection<(Of <(T>)>) can support multiple readers concurrently, as long as the collection is not modified. Even so, enumerating through a collection is intrinsically not a thread-safe procedure. To guarantee thread safety during enumeration, you can lock the collection during the entire enumeration. To allow the collection to be accessed by multiple threads for reading and writing, you must implement your own synchronization.

Would the following public static collection be safe for multiple threads to iterate over? If not, is there something built into .NET that is safe? Should I just drop the ReadOnlyCollection and create a new copy of a private collection for each access of a SomeStrings property getter? I understand that there could be a deadlock issue if multiple threads tried to lock on the public collection, but this is an internal library, and I can't see why we would ever want to.

public static class WellKnownStrings {

    public static readonly ICollection<string> SomeStrings;

    static WellKnownStrings()
    {
        Collection<string> someStrings = new Collection<string>();
        someStrings.Add("string1");
        someStrings.Add("string2");
        SomeStrings = new ReadOnlyCollection<string>(someStrings);
    }
}

Answer 1

If anyone is interesting in knowing what I ended up doing here, after seeing this answer by Jon Skeet (of course), I went with this:

public static class WellKnownStrings
{
    public const string String1= "SOME_STRING_1";

    public const string String2= "SOME_STRING_2_SPECIAL";

    public const string String3= "SOME_STRING_3_SPECIAL";

    public static IEnumerable<string> SpecialStrings
    {
        get
        {
            yield return String2;
            yield return String3;
        }
    }
}

It doesn't give callers the rest of the ICollection<T> functionality, but that's not needed in my case.