c# - Best collection to use with type Double as key

Question

I have this object:

Public Cactus{
    Public Double key;
    Public String value;
}

I have about ~100 Cactus, which all have a unique key, and a value that has some duplicates. I will however have to retrieve the value for a key about ~2000 times. My Key values varies between -10 and 280.

I want this process to be as quick as possible. What would be the best approach for this? I was thinking using a HashTable, although I always used one with Integer and not Double, and for some reason I am worried that it's not good practice to use Double as Key.

Given my scenario, which collection would be the best to use?

Answer 1

Using a double as a key in a dictionary is generally a really bad idea. You will run into all sorts of problems with representation errors where you think you stored 0.1 in the dictionary but actually you stored something very close to but not quite equal to 0.1.

I'd suggest using another type (string?) if you need exact matches.

If you don't want exact matches but just finding the closest value, consider something like a SortedList instead.