Multiple Threads Accessing Large Dictionary object in memory - bottleneck?

Question

Quick multithreading question...

I have a single dictionary object in memory containing about 20,000 items. If I have multiple threads attempting to read from this object, would you expect this to create a bottleneck?

NET 3.5 . Dictionary object would be read only

Dictionary is ReadOnly so I'm not concerned about read/writes, only performance.

Answer 1

It won't create a bottleneck but a dictionary is not thread safe so you might not get the expected results. In .NET 4.0 you could use ConcurrentDictionary<TKey, TValue> for this purpose.

If it's a readonly dictionary then it's probably safe to have concurrent readers, just make sure that you fill this dictionary with data in a static constructor to make sure that writing doesn't interfere with reading and it takes place before any thread tries to read.