Span<T> and Memory<T>

Context: Span<T> and Memory<T> are ref‑struct types introduced in .NET Core 2.1 to provide safe, allocation‑free access to contiguous memory regions. They can represent arrays, strings, or native buffers. Span<T> is stack‑only, while Memory<T> can live on the heap and be used in async methods. They are critical for high‑performance scenarios where you want to avoid copying data.

Usage Example

using System;

public class SpanDemo
{
    public static void SliceExample()
    {
        int[] numbers = { 1, 2, 3, 4, 5 };
        Span<int> span = numbers.AsSpan();
        Span<int> slice = span.Slice(1, 3); // {2,3,4}
        slice[0] = 10; // Modifies original array
        Console.WriteLine(numbers[1]); // 10
    }
}

Output console

dotnet run
10

Important notes

• Span<T> cannot be used as a field in async methods or classes.
• Memory<T> is a heap‑friendly alternative for async scenarios.

Real‑world usage example

Parsing CSV lines – Instead of allocating substrings, use Span<char> and Slice to parse comma‑separated values without allocations.
See .NET docs on Span.

Related sections

• 10.3.1 Stack‑only Span
• 10.3.2 Memory for heap or async