Creating a constant Dictionary in C#

Question

What is the most efficient way to create a constant (never changes at runtime) mapping of strings to ints?

I\'ve tried us

Answer 1

Why not:

public class MyClass
{
    private Dictionary _myCollection = new Dictionary() { { "A", 1 }, { "B", 2 }, { "C", 3 } };

    public IEnumerable> MyCollection
    {
        get { return _myCollection.AsEnumerable>(); }
    }
}