# Implementing [ ] operator

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)
{
}
}

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?

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.

• I think you mean Dictionary<string, List<object>>. – svick Jul 10 '12 at 14:14
• Yes you're right. Thanks. How do I accept your edit? – Amiram Korach Jul 10 '12 at 14:16
• 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.) – svick Jul 10 '12 at 15:01

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()
);