Hashtable with MultiDimensional Key in C#

I think a better approach is to encapsulate the many fields of your multi-dimensional key into a class / struct. For example

struct Key {
  public readonly int Dimension1;
  public readonly bool Dimension2;
  public Key(int p1, bool p2) {
    Dimension1 = p1;
    Dimension2 = p2;
  }
  // Equals and GetHashCode ommitted
}

Now you can create and use a normal HashTable and use this wrapper as a Key.

You can do this in C# 7.0 now with the new tuples:

// Declare
var test = new Dictionary<(int, bool), int>();

// Add
test.Add((1, false), 5);

// Get
int a = test[(1, false)];

How about using a regular Dictionary with some kind of Tuple structure as a key?

public class TwoKeyDictionary<K1,K2,V>
{
    private readonly Dictionary<Pair<K1,K2>, V> _dict;

    public V this[K1 k1, K2 k2]
    {
        get { return _dict[new Pair(k1,k2)]; }
    }

    private struct Pair
    {
        public K1 First;
        public K2 Second;

        public override Int32 GetHashCode()
        {
            return First.GetHashCode() ^ Second.GetHashCode();
        }

        // ... Equals, ctor, etc...
    }
}