Elegant way to create a nested Dictionary in C#

Question

I realized that I didn\'t give enough information for most people to read my mind and understand all my needs, so I changed this somewhat from the original.

Answer 1

Use BeanMap's two key Map class. There is also a 3 key map, and it is quite extensible in case you need n keys.

http://beanmap.codeplex.com/

Your solution would then look like:

class Thing
{
  public int Foo { get; set; }
  public int Bar { get; set; }
  public string Baz { get; set; }
}

[TestMethod]
public void ListToMapTest()
{
  var things = new List
             {
                 new Thing {Foo = 3, Bar = 3, Baz = "quick"},
                 new Thing {Foo = 3, Bar = 4, Baz = "brown"},
                 new Thing {Foo = 6, Bar = 3, Baz = "fox"},
                 new Thing {Foo = 6, Bar = 4, Baz = "jumps"}
             };

  var thingMap = Map.From(things, t => t.Foo, t => t.Bar, t => t.Baz);

  Assert.IsTrue(thingMap.ContainsKey(3, 4));
  Assert.AreEqual("brown", thingMap[3, 4]);

  thingMap.DefaultValue = string.Empty;
  Assert.AreEqual("brown", thingMap[3, 4]);
  Assert.AreEqual(string.Empty, thingMap[3, 6]);

  thingMap.DefaultGeneration = (k1, k2) => (k1.ToString() + k2.ToString());

  Assert.IsFalse(thingMap.ContainsKey(3, 6));
  Assert.AreEqual("36", thingMap[3, 6]);
  Assert.IsTrue(thingMap.ContainsKey(3, 6));
}