Implementing [ ] operator

Question

I have implemented the "[ ]" operator in a class that I have created to return values associated with a key (the same concept of a dictionary, except that it's possible to have the same key more than one time). However, looking at my code I don't think it is as efficient as it could be.

public class MyClass
{
 public object[][] Values;
 public MyClass()
 {
 Values = new object[4][];
 }
 public IEnumerable<object> this[string key]
 {
 get
 {
 var results = new List<object>();
 foreach (var value in this.Values)
 {
 if (value[0].ToString() == key)
 {
 results.Add(value[1]);
 }
 }
 return results;
 }
 }
}

Values can contain a bunch of 2 values arrays.

A small example:

MyClass class = new MyClass();
class.Values[0] = new object[] { "key1", 25 };
class.Values[1] = new object[] { "key2", 3 };
class.Values[2] = new object[] { "key2", 789 };
class.Values[3] = new object[] { "key4", 12 };

and when I do class["key2"], it returns a collection containing 3 and 789.

What do you think of the way I implemented the this[string key] method? Do you think there is a way to do this without iterating on all the objects in the Values array?

• Jesse C. Slicer: Read about Generics (msdn.microsoft.com/en-US/library/ms379564.aspx) and favor them over storing items of type object.

Answer 1

If you look for performance, you'd better rely on the framework dictionary. You can use the Dictionary<string, List<object>> to do what you need. When you add a new key and value, look if the key already exists. If so, add the value to the array and don't add the key.

• svick: I think you mean Dictionary<string, List<object>>.
• Amiram Korach: Yes you're right. Thanks. How do I accept your edit?
• svick: I didn't propose that edit, you could have just edited your answer by yourself. (I have enough reputation on this site, so that my edits are accepted automatically. If I didn't and I made that edit, you would see a number beside the "edit" button, signifying how many people already accepted the edit.)

Answer 2

This is intended as a comment to the answer from @AmiramKorach; here is a reasonable way to get from the list you have to the dictionary you want (without concerning yourself about managing the dictionary details):

Dictionary<string, List<int>> result =
 new[]
 {
 new {Name = "key1", Value = 25},
 new {Name = "key2", Value = 3},
 new {Name = "key2", Value = 789},
 new {Name = "key3", Value = 12}
 }
 .GroupBy(p => p.Name)
 .ToDictionary(
 group => group.Key,
 values => values.Select(g => g.Value).ToList()
 );