I would like to know if some property or method exists that gets the index of a specific value.
I found that dictionaries have the
There's no such concept of an "index" within a dictionary - it's fundamentally unordered. Of course when you iterate over it you'll get the items in some order, but that order isn't guaranteed and can change over time (particularly if you add or remove entries).
Obviously you can get the key from a
KeyValuePair just by using the
Key property, so that will let you use the indexer of the dictionary:
var pair = ...; var value = dictionary[pair.Key]; Assert.AreEqual(value, pair.Value);
You haven't really said what you're trying to do. If you're trying to find some key which corresponds to a particular value, you could use:
var key = dictionary.Where(pair => pair.Value == desiredValue) .Select(pair => pair.Key) .FirstOrDefault();
key will be null if the entry doesn't exist.
This is assuming that the key type is a reference type... if it's a value type you'll need to do things slightly differently.
Of course, if you really want to look up values by key, you should consider using another dictionary which maps the other way round in addition to your existing dictionary.