UserAgent.cs

using System;

/// <summary>
/// Random User Agent Generator (invented by gigajew)
/// </summary>
public class UserAgent
{
    /// <summary>
    /// System.Random
    /// </summary>
    private static Random _random;

    /// <summary>
    /// Static constructor (.cctor)
    /// </summary>
    static UserAgent()
    {
        _random = new Random(Guid.NewGuid().GetHashCode());
    }

    /// <summary>
    /// OS type
    /// </summary>
    public enum System : Int32
    {
        Windows = 0, Macintosh = 1, X11 = 2, iPad = 3, Unknown = 4
    }

    /// <summary>
    /// Get a random user-agent
    /// </summary>
    /// <returns></returns>
    public static string GetRandomUserAgent()
    {
        return $"Mozilla/5.0 {GetRandomSystem()} {GetRandomRenderEngine()} {GetRandomBrowser()}";
    }

    /// <summary>
    /// Convert System to String
    /// </summary>
    /// <param name="system"></param>
    /// <returns></returns>
    private static string GetSystem(System system)
    {
        if (system == System.Windows)
        {
            return $"(Windows NT {GetRandomVersion(10)}; {GetRandomArchitecture(system)})";
        }
        else if (system == System.Macintosh)
        {
            return $"(Macintosh; Intel Mac OS X 10_{_random.Next(9, 14)}_{_random.Next(0, 11)})";
        }
        else if (system == System.Unknown)
        {
            return $"(compatible; MSIE {GetRandomVersion(10)}; Windows NT {GetRandomVersion(10)}; Trident/{GetRandomVersion(5)}; Trident/{GetRandomVersion(5)})";
        }
        else if (system == System.iPad)
        {
            return $"(iPad; CPU OS 10_{_random.Next(1, 14)}_{_random.Next(0, 11)} like Mac OS X)";
        }
        else if (system == System.X11)
        {
            if (_random.Next(0, 2) == 1)
            {
                return $"(X11; Ubuntu; Linux x86_64; rv:{GetRandomVersion(80)})";
            }
            else
            {
                return $"(X11; Linux x86_64; rv:{GetRandomVersion(80)})";
            }
        }
        return string.Empty;
    }

    /// <summary>
    /// Return a random OS type
    /// </summary>
    /// <returns></returns>
    private static string GetRandomSystem()
    {
        var sys = (System)_random.Next(0, 5);
        return GetSystem(sys);
    }

    /// <summary>
    /// Get random architecture
    /// </summary>
    /// <param name="system"></param>
    /// <returns></returns>
    private static string GetRandomArchitecture(System system)
    {
        var i = _random.Next(0, 2);
        if (system == System.Windows)
        {
            return (i == 1) ? "Win64; x64" : $"WOW64; rv:{GetRandomVersion(80)}";
        }
        return string.Empty;
    }

    /// <summary>
    /// Get random browser
    /// </summary>
    /// <returns></returns>
    private static string GetRandomBrowser()
    {
        int i = _random.Next(0, 3);
        if (i == 0)
        {
            return $"(KHTML, like Gecko) Chrome/{_random.Next(30, 90)}.0.{_random.Next(1000, 3000)}.{_random.Next(100, 200)} Safari/{_random.Next(400, 600)}.{_random.Next(20, 50)}";
        }
        else if (i == 1)
        {
            return $"Firefox/{_random.Next(40, 60)}.0";
        }
        else if (i == 2)
        {
            return $"(KHTML, like Gecko) Version/{_random.Next(1, 11)}.0 Mobile/14G60 Safari/{GetRandomVersion(600)}";
        }
        return string.Empty;
    }

    /// <summary>
    /// Get random render engine
    /// </summary>
    /// <returns></returns>
    private static string GetRandomRenderEngine()
    {
        int i = _random.Next(0, 2);
        if (i == 1)
        {
            return $"AppleWebKit/{GetRandomVersion(1000)}.{_random.Next(1, 10)}.{_random.Next(1, 10)}";
        }
        else
        {
            return "Gecko/20100101";
        }
    }

    /// <summary>
    /// Get random float (version) X.x
    /// </summary>
    /// <param name="max"></param>
    /// <returns></returns>
    private static double GetRandomVersion(int max)
    {
        return Math.Round(_random.NextDouble() * (max + 2), 1);
    }
}