Bidirectional Map in .NET

Question

Is there a .NET data structure I could use for bidirectional lookup?

Here's the problem: Serialization. My object contains a field which points to one of 10 predefined static objects. When writing to the file, I write a single character representing which of the 10 objects is being referenced. At this point, I need a lookup datastructure which will allow me to get the character code based on the object being referenced. When deserializing, I need to do the reverse. I can think of a lot of other places where I could use such a data structure.

Answer 1

In the case of only 10 cases that will rarely change, a couple of methods using Switch statements would probably suffice.

If you have control of the static objects, then they could all implement a new interface that returns a "serialization code" character:

public interface IStaticObject
{
    char SerializationCode { get; };
}

Therefore, going in that direction is easy: someObject.SerializationCode. Then you could also have your static objects all use a constructor that registers their SerializationCode with a singleton instance that has a Dictionary.

public class SomeStaticObject : IStaticObject
{
    public void SomeStaticObject()
    {
        StaticObjectRegistrar.Register(this.SerializationCode, this);
    }

    public char SerializationCode
    {
        get
        {
            return ?;
        }
    }
}

Deserializing, you just take the character and run it through that dictionary to get the static object back.

Answer 2

I would create a data structure that contains two generic Dictionary objects that mirror each other in such a way that the key of one represents the value of the other and vice versa. This would allow for O(1) lookup in both directions.