Working with spans, indexes, and ranges

One of Microsoft's goals with .NET Core 2.1 was to improve performance and resource usage. A key .NET feature that enables this is the Span<T> type.

Using memory efficiently using spans

When manipulating arrays, you will often create new copies or subsets of existing ones so that you can process just the subset. This is not efficient because duplicate objects must be created in memory.

If you need to work with a subset of an array, use a span because it is like a window into the original array. This is more efficient in terms of memory usage and improves performance. Spans only work with arrays, not collections, because the memory must be contiguous.

Before we look at spans in more detail, we need to understand some related objects: indexes and ranges.

Identifying positions with the Index type

C# 8 introduced two features for identifying an item's index position within an array and a range of items using two indexes.

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