Is there a way to trim a Dictionary's capacity once it is known to be fixed size?

Question

After reading the excellent accepted answer in this question:

How is the c#/.net 3.5 dictionary implemented?

I decided to set my initial capacity to a large guess and then trim it after I read in all values. How can I do this? That is, how can I trim a Dictionary so the gc will collect the unused space later?

My goal with this is optimization. I often have large datasets and the time penalty for small datasets is acceptable. I want to avoid the overhead of reallocating and copying the data that is incured with small initial capacities on large datasets.

Answer 1

According to Reflector, the Dictionary class never shrinks. void Resize() is hard-coded to always double the size.

You can probably create a new dictionary and use the respective constructor to copy over the items. This will be quite inefficient.

Or, implement your own dictionary with the existing one as a blue-print. This is less work than you might think at first.

Be sure to benchmark both approaches.