Middleware to block bad bots in ASP.NET 5

BadBotMiddleWare.cs

public class BadBotMiddleWare
{
    private readonly RequestDelegate _next;
    public ImmutableHashSet<string> List { get; set; }

    public BadBotMiddleWare(RequestDelegate next)
    {
        _next = next;
        List = new[]
        {
            "Aboundex",
            "80legs",
            "360Spider",
            "Java",
            "Cogentbot",
            "Alexibot",
            "asterias",
            "attach",
            "BackDoorBot",
            "BackWeb",
            "Bandit",
            "BatchFTP",
            "Bigfoot",
            "Black.Hole",
            "BlackWidow",
            "BlowFish",
            "BotALot",
            "Buddy",
            "BuiltBotTough",
            "Bullseye",
            "BunnySlippers",
            "Cegbfeieh",
            "CheeseBot",
            "CherryPicker",
            "ChinaClaw",
            "Collector",
            "Copier",
            "CopyRightCheck",
            "cosmos",
            "Crescent",
            "Custo",
            "AIBOT",
            "DISCo",
            "DIIbot",
            "DittoSpyder",
            "Download\\ Demon",
            "Download\\ Devil",
            "Download\\ Wonder",
            "dragonfly",
            "Drip",
            "eCatch",
            "EasyDL",
            "ebingbong",
            "EirGrabber",
            "EmailCollector",
            "EmailSiphon",
            "EmailWolf",
            "EroCrawler",
            "Exabot",
            "Express\\ WebPictures",
            "Extractor",
            "EyeNetIE",
            "Foobot",
            "flunky",
            "FrontPage",
            "Go-Ahead-Got-It",
            "gotit",
            "GrabNet",
            "Grafula",
            "Harvest",
            "hloader",
            "HMView",
            "HTTrack",
            "humanlinks",
            "IlseBot",
            "Image\\ Stripper",
            "Image\\ Sucker",
            "Indy\\ Library",
            "InfoNaviRobot",
            "InfoTekies",
            "Intelliseek",
            "InterGET",
            "Internet\\ Ninja",
            "Iria",
            "Jakarta",
            "JennyBot",
            "JetCar",
            "JOC",
            "JustView",
            "Jyxobot",
            "Kenjin.Spider",
            "Keyword.Density",
            "larbin",
            "LexiBot",
            "lftp",
            "libWeb/clsHTTP",
            "libwhisker",
            "libwww-perl",
            "likse",
            "LinkextractorPro",
            "LinkScan/8.1a.Unix",
            "LNSpiderguy",
            "LinkWalker",
            "lwp-trivial",
            "LWP::Simple",
            "Magnet",
            "Mag-Net",
            "MarkWatch",
            "Mass\\ Downloader",
            "Mata.Hari",
            "Memo",
            "Microsoft.URL",
            "Microsoft\\ URL\\ Control",
            "MIDown\\ tool",
            "MIIxpc",
            "Mirror",
            "Missigua\\ Locator",
            "Mister\\ PiX",
            "moget",
            "Mozilla/3.Mozilla/2.01",
            "Mozilla.*NEWT",
            "NAMEPROTECT",
            "Navroad",
            "NearSite",
            "NetAnts",
            "Netcraft",
            "NetMechanic",
            "NetSpider",
            "Net\\ Vampire",
            "NetZIP",
            "NextGenSearchBot",
            "NG",
            "NICErsPRO",
            "niki-bot",
            "NimbleCrawler",
            "Ninja",
            "NPbot",
            "Octopus",
            "Offline\\ Explorer",
            "Offline\\ Navigator",
            "Openfind",
            "OutfoxBot",
            "PageGrabber",
            "Papa\\ Foto",
            "pavuk",
            "pcBrowser",
            "PHP\\ version\\ tracker",
            "Pockey",
            "ProPowerBot/2.14",
            "ProWebWalker",
            "psbot",
            "Pump",
            "QueryN.Metasearch",
            "RealDownload",
            "Reaper",
            "Recorder",
            "ReGet",
            "RepoMonkey",
            "RMA",
            "Siphon",
            "SiteSnagger",
            "SlySearch",
            "SmartDownload",
            "Snake",
            "Snapbot",
            "Snoopy",
            "sogou",
            "SpaceBison",
            "SpankBot",
            "spanner",
            "Sqworm",
            "Stripper",
            "Sucker",
            "SuperBot",
            "SuperHTTP",
            "Surfbot",
            "suzuran",
            "Szukacz/1.4",
            "tAkeOut",
            "Teleport",
            "Telesoft",
            "TurnitinBot/1.5",
            "The.Intraformant",
            "TheNomad",
            "TightTwatBot",
            "Titan",
            "True_Robot",
            "turingos",
            "TurnitinBot",
            "URLy.Warning",
            "Vacuum",
            "VCI",
            "VoidEYE",
            "Web\\ Image\\ Collector",
            "Web\\ Sucker",
            "WebAuto",
            "WebBandit",
            "Webclipping.com",
            "WebCopier",
            "WebEMailExtrac.*",
            "WebEnhancer",
            "WebFetch",
            "WebGo\\ IS",
            "Web.Image.Collector",
            "WebLeacher",
            "WebmasterWorldForumBot",
            "WebReaper",
            "WebSauger",
            "Website\\ eXtractor",
            "Website\\ Quester",
            "Webster",
            "WebStripper",
            "WebWhacker",
            "WebZIP",
            "Whacker",
            "Widow",
            "WISENutbot",
            "WWWOFFLE",
            "WWW-Collector-E",
            "Xaldon",
            "Xenu",
            "Zeus",
            "ZmEu",
            "Zyborg",
            "Acunetix",
            "FHscan",
            "Baiduspider",
            "Yandex"
        }.ToImmutableHashSet();
    }

    public async Task Invoke(HttpContext context)
    {
        if (List.Any(s => context?.Request?.Headers["User-Agent"].ToString().IndexOf(s, StringComparison.OrdinalIgnoreCase) >=0))
        {
            return;
        }

        await _next(context);
    }
}