C#: How do you use Span<T> and Memory<T> in C#?

1// Slice without allocation
2Span<char> span = stackalloc char[256];
3"Hello World".AsSpan().CopyTo(span);
4
5// String slicing
6ReadOnlySpan<char> hello = "Hello World".AsSpan(0, 5);

1Memory<byte> buffer = new byte[1024];
2Memory<byte> slice = buffer.Slice(0, 512);
3await stream.ReadAsync(buffer);

1var reader = PipeReader.Create(stream);
2ReadResult result = await reader.ReadAsync();
3ReadSequence<byte> sequence = result.Buffer;