I have dictionary containing key value pairs.
SortedDictionary<int,int> dictionary=new SortedDictionary<int,int>();
dictionary.Add(1,33);
dictionary.Add(2,20);
dictionary.Add(4,35);
I want to get previous key value pair from a known key value. In the above case, if I have key 4, then how can I get <2,20>?
You could loop through the dictionary and keep track of values, I guess. Something like this:
public int GetPreviousKey(int currentKey, SortedDictionary<int, int> dictionary)
{
int previousKey = int.MinValue;
foreach(KeyValuePair<int,int> pair in dictionary)
{
if(pair.Key == currentKey)
{
if(previousKey == int.MinValue)
{
throw new InvalidOperationException("There is no previous key.");
}
return previousKey;
}
else
{
previousKey = pair.Key;
}
}
}
However, this is a pretty odd operation to require. The fact that you need it might be pointing at a problem with your design.
How about this? I havent tested it though, but should give something to start think in this direction. Hope it helps.
int input = 4;
List<int> lKeys = dictionary.Keys.ToList();
int reqIndex = lKeys.IndexOf(input) - 1;
int reqAnswer = dictionary[reqIndex];
test for other conditions like if (reqIndex != -1) etc..