Fast Lookup in List

Question

Hi everyone i've got a problem using Generic.List. I'm currently writing a program which has to deal with a lot of data stored in a Generic.List. I often need to search through the list to find out if a new item is already stored in the list. This is no problem beacause of the Contains-Method. The problem is this method is very slow and the processing has to be very fast. I've come up with writing an anonymous function which does the seacrhing for me whcih is way faster. looking like this: col = getNewColor(); if (!colors.Exists(delegate(Color c) { return c == col; })) { colors.Add(col); }// This is also not that fast concerning what I need for my programm. Is there any way to speed-up a search through a list? I appreciate any help. Greetings LeRoi

Brandon Lewis · Answer

Have you tried implementing a binary search on the generic collection? Any array can implement a binary search or you can create your own if necessary.

Robert · Answer

I've tried that but it's as fast as the delegate. I've now come up with a Dictionary which is way faster using the ContainsKey-Method which uses hashing. Greets LeRoi

Alan · Answer

Don't laugh but have you tried a simple traversal of the list using a for (not foreach) loop which is often the fastest method of all as there's virtually no overhead: col = getNewColor(); bool exists = false; for(int i = 0; i { if (colors[i] == col) { exists = true; break; } } if (!exists) { colors.Add(col); }