Starting a specific Firefox Profile with Selenium 3

This exception is due to a bug in the .Net library. The code generating the Zip of the profile is failing to provide a proper Zip.

One way to overcome this issue would be to overload FirefoxOptions and use the archiver from .Net framework (System.IO.Compression.ZipArchive) instead of the faulty ZipStorer:

var options = new FirefoxOptionsEx();options.Profile = @"C:\Users\...\AppData\Roaming\Mozilla\Firefox\Profiles\ez3krw80.Selenium";options.SetPreference("network.proxy.type", 0);var service = FirefoxDriverService.CreateDefaultService(@"C:\downloads", "geckodriver.exe");var driver = new FirefoxDriver(service, options, TimeSpan.FromMinutes(1));

class FirefoxOptionsEx : FirefoxOptions {    public new string Profile { get; set; }    public override ICapabilities ToCapabilities() {        var capabilities = (DesiredCapabilities)base.ToCapabilities();        var options = (IDictionary)capabilities.GetCapability("moz:firefoxOptions");        var mstream = new MemoryStream();        using (var archive = new ZipArchive(mstream, ZipArchiveMode.Create, true)) {            foreach (string file in Directory.EnumerateFiles(Profile, "*", SearchOption.AllDirectories)) {                string name = file.Substring(Profile.Length + 1).Replace('\\', '/');                if (name != "parent.lock") {                    using (Stream src = File.OpenRead(file), dest = archive.CreateEntry(name).Open())                        src.CopyTo(dest);                }            }        }        options["profile"] = Convert.ToBase64String(mstream.GetBuffer(), 0, (int)mstream.Length);        return capabilities;    }}

And to get the directory for a profile by name:

var manager = new FirefoxProfileManager();var profiles = (Dictionary<string, string>)manager.GetType()    .GetField("profiles", BindingFlags.Instance | BindingFlags.NonPublic)    .GetValue(manager);string directory;if (profiles.TryGetValue("Selenium", out directory))    options.Profile = directory;