.NET Core 2 Span and Memory

.NET Core 2.1 includes some new types that make working with arrays and other memory types much more efficient. The new types include:

• System.Span<T>: Provides a type- and memory-safe representation of a contiguous region of arbitrary memory.
• System.ReadOnlySpan<T>: Provides a type-safe and memory-safe read-only representation of a contiguous region of arbitrary memory.
• System.Memory<T>: Represents a contiguous region of memory.
• System.ReadOnlyMemory<T>: Represents a contiguous region of memory, similar to ReadOnlySpan<T>. Unlike ReadOnlySpan<T>, it is not a by ref like type.

Without these types, when passing such items as a portion of an array or a section of a memory buffer, you have to copy some portion of the data before passing it to a method. These types provide a virtual view of that data that eliminates the need for additional memory allocation and copy operations.

The following example uses a Span<T> and Memory<T> instance to provide a virtual view of 10 elements of an array.

int[] numbers = new int[100];
for (int i = 0; i < 100; i++)
{
    numbers[i] = i * 2;
}

var part = new Span<int>(numbers, start: 10, length: 10);

foreach (var value in part)
{
    Console.Write($"{value}  ");
}

When you run the above example, you will see the following output.

20  22  24  26  28  30  32  34  36  38