.NET 8 has introduced new empty collections that you can use to reduce your memory usage and speed up your runtime.  Often, if you want to return an empty collection such as a List<T> or Dictionary<K,T> you need to new up a new instance.  The downside is memory is allocated.  This might not be a big deal but then again, if that code is executed thousands of times, the memory usage and processing time adds up.  Just how much?  Well, it is a non-trivial amount for applications looking to maximize performance.

I created a simple .NET Core console app using the .NET 8 preview along with BenchmarkDotNet to measure the difference between the old approach vs. new. 

Some example code:

[Benchmark]
public IReadOnlyDictionary<int, User> Dictionary_New()
{
    return ReadOnlyDictionary<int, User>.Empty;
}

[Benchmark]
public IReadOnlyDictionary<int, User> Dictionary_Old()
{
    return new Dictionary<int, User>();
}

Here are the results:

As you can see, the run time and memory usage between old and new is non-trivial and going forward, I plan to use these new empty collections.

My sample app with the full source code is available on GitHub - https://github.com/cliffordru/BenchmarkEmptyCollections

Need a developer, architect or manager? I am available - email me at [email protected]