Method to Add new or update existing item in Dictionary
There's no problem. I would even remove the CreateNewOrUpdateExisting from the source and use map[key] = value directly in your code, because this this idiomatic C#; C# developers would typically know that map[key] = value means add or update.
Could there be any problem if i replace Method-1 by Method-2?
No, just use map[key] = value. The two options are equivalent.
Regarding Dictionary<> vs. Hashtable: When you start Reflector, you see that the indexer setters of both classes call this.Insert(key, value, add: false); and the add parameter is responsible for throwing an exception, when inserting a duplicate key. So the behavior is the same for both classes.
Old question but i feel i should add the following, even more because .net 4.0 had already launched at the time the question was written.
Starting with .net 4.0 there is the namespace System.Collections.Concurrent which includes collections that are thread-safe.
The collection System.Collections.Concurrent.ConcurrentDictionary<> does exactly what you want. It has the AddOrUpdate() method with the added advantage of being thread-safe.
If you're in a high-performance scenario and not handling multiple threads the already given answers of map[key] = value are faster.
In most scenarios this performance benefit is insignificant. If so i'd advise to use the ConcurrentDictionary because:
- It is in the framework - It is more tested and you are not the one who has to maintain the code
- It is scalable: if you switch to multithreading your code is already prepared for it