When working with Span<char> or ReadOnlySpan<char> for zero-allocation string processing, comparing against known string values required calling MemoryExtensions.SequenceEqual or similar methods.

C# 11 allows you to use is and switch to pattern match a Span<char> or ReadOnlySpan<char> directly against a string constant.

Code

Now

static int ParseCommand(ReadOnlySpan<char> command) => command switch
{
    "start" => 1,
    "stop" => 2,
    "reset" => 3,
    _ => -1
};

Before

static int ParseCommand(ReadOnlySpan<char> command)
{
    if (command.SequenceEqual("start")) return 1;
    if (command.SequenceEqual("stop")) return 2;
    if (command.SequenceEqual("reset")) return 3;
    return -1;
}

More information

• What's New in C# 11