Is there an IDictionary implementation that, on missing key, returns the default value instead of throwing?

Question

The indexer into Dictionary throws an exception if the key is missing. Is there an implementation of IDictionary that instead will return de

Answer 1

Collections.Specialized.StringDictionary provides a non-exception result when looking up a missing key's value. It is also case-insensitive by default.

Caveats

It is only valid for its specialized uses, and — being designed before generics — it doesn't have a very good enumerator if you need to review the whole collection.

Answer 2

What about this one-liner that checks whether a key is present using ContainsKey and then returns either the normally retreived value or the default value using the conditional operator?

var myValue = myDictionary.ContainsKey(myKey) ? myDictionary[myKey] : myDefaultValue;

No need to implement a new Dictionary class that supports default values, simply replace your lookup statements with the short line above.

Answer 3

It could be a one-liner to check TryGetValue and return default value if it is false.

 Dictionary<string, int> myDic = new Dictionary<string, int>() { { "One", 1 }, { "Four", 4} };
 string myKey = "One"
 int value = myDic.TryGetValue(myKey, out value) ? value : 100;

myKey = "One" => value = 1

myKey = "two" => value = 100

myKey = "Four" => value = 4

Try it online