sharplab example fo F# DUs in C#

Domain.fs

type PhoneOS = Android | Apple

type ThingIOwn = 
| Car of make: string * model: string * year: string
| Phone of OS: PhoneOS * model: string

let thing = Phone(Android, "Pixel 2XL")

Sample.cs

using System;
using System.Collections;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

[Serializable]
[StructLayout(LayoutKind.Auto, CharSet = CharSet.Auto)]
public sealed class PhoneOS : IEquatable<PhoneOS>, IStructuralEquatable, IComparable<PhoneOS>, IComparable, IStructuralComparable
{
    public static class Tags
    {
        public const int Android = 0;

        public const int Apple = 1;
    }

    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    [CompilerGenerated]
    internal readonly int _tag;

    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    [CompilerGenerated]
    internal static readonly PhoneOS _unique_Android = new PhoneOS(0);

    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    [CompilerGenerated]
    internal static readonly PhoneOS _unique_Apple = new PhoneOS(1);

    [CompilerGenerated]
    [DebuggerNonUserCode]
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    public int Tag
    {
        [CompilerGenerated]
        [DebuggerNonUserCode]
        get
        {
            return _tag;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    public static PhoneOS Android
    {
        get
        {
            return _unique_Android;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    public bool IsAndroid
    {
        [CompilerGenerated]
        [DebuggerNonUserCode]
        get
        {
            return Tag == 0;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    public static PhoneOS Apple
    {
        get
        {
            return _unique_Apple;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    public bool IsApple
    {
        [CompilerGenerated]
        [DebuggerNonUserCode]
        get
        {
            return Tag == 1;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    internal PhoneOS(int _tag)
    {
        this._tag = _tag;
    }

    [CompilerGenerated]
    public int CompareTo(PhoneOS obj)
    {
        if (this != null)
        {
            if (obj != null)
            {
                int tag = _tag;
                int tag2 = obj._tag;
                if (tag == tag2)
                {
                    return 0;
                }
                return tag - tag2;
            }
            return 1;
        }
        if (obj != null)
        {
            return -1;
        }
        return 0;
    }

    [CompilerGenerated]
    public int CompareTo(object obj)
    {
        return CompareTo((PhoneOS)obj);
    }

    [CompilerGenerated]
    public int CompareTo(object obj, IComparer comp)
    {
        PhoneOS phoneOS = (PhoneOS)obj;
        if (this != null)
        {
            if ((PhoneOS)obj != null)
            {
                int tag = _tag;
                int tag2 = phoneOS._tag;
                if (tag == tag2)
                {
                    return 0;
                }
                return tag - tag2;
            }
            return 1;
        }
        if ((PhoneOS)obj != null)
        {
            return -1;
        }
        return 0;
    }

    [CompilerGenerated]
    public int GetHashCode(IEqualityComparer comp)
    {
        if (this != null)
        {
            return _tag;
        }
        return 0;
    }

    [CompilerGenerated]
    public bool Equals(object obj, IEqualityComparer comp)
    {
        if (this != null)
        {
            PhoneOS phoneOS = obj as PhoneOS;
            if (phoneOS != null)
            {
                int tag = _tag;
                int tag2 = phoneOS._tag;
                return tag == tag2;
            }
            return false;
        }
        return obj == null;
    }

    [CompilerGenerated]
    public bool Equals(PhoneOS obj)
    {
        if (this != null)
        {
            if (obj != null)
            {
                int tag = _tag;
                int tag2 = obj._tag;
                return tag == tag2;
            }
            return false;
        }
        return obj == null;
    }

    [CompilerGenerated]
    public sealed override bool Equals(object obj)
    {
        PhoneOS phoneOS = obj as PhoneOS;
        if (phoneOS != null)
        {
            return Equals(phoneOS);
        }
        return false;
    }
}

[Serializable]
[StructLayout(LayoutKind.Auto, CharSet = CharSet.Auto)]
public abstract class ThingIOwn : IEquatable<ThingIOwn>, IStructuralEquatable, IComparable<ThingIOwn>, IComparable, IStructuralComparable
{
    public static class Tags
    {
        public const int Car = 0;

        public const int Phone = 1;
    }

    [Serializable]
    public class Car : ThingIOwn
    {
        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [CompilerGenerated]
        internal readonly string _make;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [CompilerGenerated]
        internal readonly string _model;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [CompilerGenerated]
        internal readonly string _year;

        [CompilerGenerated]
        [DebuggerNonUserCode]
        public string make
        {
            [CompilerGenerated]
            [DebuggerNonUserCode]
            get
            {
                return _make;
            }
        }

        [CompilerGenerated]
        public string model
        {
            [CompilerGenerated]
            get
            {
                return _model;
            }
        }

        [CompilerGenerated]
        public string year
        {
            [CompilerGenerated]
            get
            {
                return _year;
            }
        }

        [CompilerGenerated]
        internal Car(string _make, string _model, string _year)
        {
            this._make = _make;
            this._model = _model;
            this._year = _year;
        }
    }

    [Serializable]
    public class Phone : ThingIOwn
    {
        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [CompilerGenerated]
        internal readonly PhoneOS oS;

        [DebuggerBrowsable(DebuggerBrowsableState.Never)]
        [CompilerGenerated]
        internal readonly string _model;

        [CompilerGenerated]
        public PhoneOS OS
        {
            [CompilerGenerated]
            get
            {
                return oS;
            }
        }

        [CompilerGenerated]
        public string model
        {
            [CompilerGenerated]
            get
            {
                return _model;
            }
        }

        [CompilerGenerated]
        internal Phone(PhoneOS oS, string _model)
        {
            this.oS = oS;
            this._model = _model;
        }
    }
    
    [CompilerGenerated]
    [DebuggerNonUserCode]
    public int Tag
    {
        [CompilerGenerated]
        [DebuggerNonUserCode]
        get
        {
            return (this is Phone) ? 1 : 0;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    public bool IsCar
    {
        [CompilerGenerated]
        [DebuggerNonUserCode]
        get
        {
            return this is Car;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    public bool IsPhone
    {
        [CompilerGenerated]
        [DebuggerNonUserCode]
        get
        {
            return this is Phone;
        }
    }

    [CompilerGenerated]
    [DebuggerNonUserCode]
    internal ThingIOwn()
    {
    }

	public static ThingIOwn NewCar(string _make, string _model, string _year)
    {
        return new Car(_make, _model, _year);
    }

    public static ThingIOwn NewPhone(PhoneOS oS, string _model)
    {
        return new Phone(oS, _model);
    }

    [CompilerGenerated]
    public int CompareTo(ThingIOwn obj)
    {
        if (this != null)
        {
            if (obj != null)
            {
                int num = (this is Phone) ? 1 : 0;
                int num2 = (obj is Phone) ? 1 : 0;
                if (num == num2)
                {
                    int num3;
                    if (this is Car)
                    {
                        Car car = (Car)this;
                        Car car2 = (Car)obj;
                        num3 = string.CompareOrdinal(car._make, car2._make);
                        if (num3 < 0)
                        {
                            return num3;
                        }
                        if (num3 > 0)
                        {
                            return num3;
                        }
                        int num4 = string.CompareOrdinal(car._model, car2._model);
                        if (num4 < 0)
                        {
                            return num4;
                        }
                        if (num4 > 0)
                        {
                            return num4;
                        }
                        return string.CompareOrdinal(car._year, car2._year);
                    }
                    Phone phone = (Phone)this;
                    Phone phone2 = (Phone)obj;
                    PhoneOS oS = phone.oS;
                    PhoneOS oS2 = phone2.oS;
                    num3 = oS.CompareTo(oS2);
                    if (num3 < 0)
                    {
                        return num3;
                    }
                    if (num3 > 0)
                    {
                        return num3;
                    }
                    return string.CompareOrdinal(phone._model, phone2._model);
                }
                return num - num2;
            }
            return 1;
        }
        if (obj != null)
        {
            return -1;
        }
        return 0;
    }

    [CompilerGenerated]
    public int CompareTo(object obj)
    {
        return CompareTo((ThingIOwn)obj);
    }

    [CompilerGenerated]
    public int CompareTo(object obj, IComparer comp)
    {
        ThingIOwn thingIOwn = (ThingIOwn)obj;
        if (this != null)
        {
            if ((ThingIOwn)obj != null)
            {
                int num = (this is Phone) ? 1 : 0;
                ThingIOwn thingIOwn2 = thingIOwn;
                int num2 = (thingIOwn2 is Phone) ? 1 : 0;
                if (num == num2)
                {
                    int num3;
                    if (this is Car)
                    {
                        Car car = (Car)this;
                        Car car2 = (Car)thingIOwn;
                        num3 = string.CompareOrdinal(car._make, car2._make);
                        if (num3 < 0)
                        {
                            return num3;
                        }
                        if (num3 > 0)
                        {
                            return num3;
                        }
                        int num4 = string.CompareOrdinal(car._model, car2._model);
                        if (num4 < 0)
                        {
                            return num4;
                        }
                        if (num4 > 0)
                        {
                            return num4;
                        }
                        return string.CompareOrdinal(car._year, car2._year);
                    }
                    Phone phone = (Phone)this;
                    Phone phone2 = (Phone)thingIOwn;
                    PhoneOS oS = phone.oS;
                    PhoneOS oS2 = phone2.oS;
                    num3 = oS.CompareTo(oS2, comp);
                    if (num3 < 0)
                    {
                        return num3;
                    }
                    if (num3 > 0)
                    {
                        return num3;
                    }
                    return string.CompareOrdinal(phone._model, phone2._model);
                }
                return num - num2;
            }
            return 1;
        }
        if ((ThingIOwn)obj != null)
        {
            return -1;
        }
        return 0;
    }

    [CompilerGenerated]
    public int GetHashCode(IEqualityComparer comp)
    {
        if (this != null)
        {
            int num = 0;
            string year;
            if (this is Car)
            {
                Car car = (Car)this;
                num = 0;
                year = car._year;
                num = -1640531527 + (((year != null) ? year.GetHashCode() : 0) + ((num << 6) + (num >> 2)));
                year = car._model;
                num = -1640531527 + (((year != null) ? year.GetHashCode() : 0) + ((num << 6) + (num >> 2)));
                year = car._make;
                return -1640531527 + (((year != null) ? year.GetHashCode() : 0) + ((num << 6) + (num >> 2)));
            }
            Phone phone = (Phone)this;
            num = 1;
            year = phone._model;
            num = -1640531527 + (((year != null) ? year.GetHashCode() : 0) + ((num << 6) + (num >> 2)));
            return -1640531527 + (phone.oS.GetHashCode(comp) + ((num << 6) + (num >> 2)));
        }
        return 0;
    }


    [CompilerGenerated]
    public bool Equals(object obj, IEqualityComparer comp)
    {
        if (this != null)
        {
            ThingIOwn thingIOwn = obj as ThingIOwn;
            if (thingIOwn != null)
            {
                int num = (this is Phone) ? 1 : 0;
                ThingIOwn thingIOwn2 = thingIOwn;
                int num2 = (thingIOwn2 is Phone) ? 1 : 0;
                if (num == num2)
                {
                    if (this is Car)
                    {
                        Car car = (Car)this;
                        Car car2 = (Car)thingIOwn;
                        if (string.Equals(car._make, car2._make))
                        {
                            if (string.Equals(car._model, car2._model))
                            {
                                return string.Equals(car._year, car2._year);
                            }
                            return false;
                        }
                        return false;
                    }
                    Phone phone = (Phone)this;
                    Phone phone2 = (Phone)thingIOwn;
                    PhoneOS oS = phone.oS;
                    PhoneOS oS2 = phone2.oS;
                    if (oS.Equals(oS2, comp))
                    {
                        return string.Equals(phone._model, phone2._model);
                    }
                    return false;
                }
                return false;
            }
            return false;
        }
        return obj == null;
    }

    [CompilerGenerated]
    public bool Equals(ThingIOwn obj)
    {
        if (this != null)
        {
            if (obj != null)
            {
                int num = (this is Phone) ? 1 : 0;
                int num2 = (obj is Phone) ? 1 : 0;
                if (num == num2)
                {
                    if (this is Car)
                    {
                        Car car = (Car)this;
                        Car car2 = (Car)obj;
                        if (string.Equals(car._make, car2._make))
                        {
                            if (string.Equals(car._model, car2._model))
                            {
                                return string.Equals(car._year, car2._year);
                            }
                            return false;
                        }
                        return false;
                    }
                    Phone phone = (Phone)this;
                    Phone phone2 = (Phone)obj;
                    if (phone.oS.Equals(phone2.oS))
                    {
                        return string.Equals(phone._model, phone2._model);
                    }
                    return false;
                }
                return false;
            }
            return false;
        }
        return obj == null;
    }

    [CompilerGenerated]
    public sealed override bool Equals(object obj)
    {
        ThingIOwn thingIOwn = obj as ThingIOwn;
        if (thingIOwn != null)
        {
            return Equals(thingIOwn);
        }
        return false;
    }
}
	
static class Startup {
 public static void Main() {
     var thing = ThingIOwn.NewPhone(PhoneOS.Android, "Pixel 2L");
     
     // can use with switch statements:
	switch (thing) {
        case ThingIOwn.Car car1:
             Console.WriteLine($"I have a {car1.year} {car1.make} {car1.model}");
             break;
     	case ThingIOwn.Phone phone:
             Console.WriteLine($"I have a {phone.model} running {phone.OS}");
             break;
     }
     
     // or use with type-based matching
     if (thing is ThingIOwn.Car car) {
     	Console.WriteLine($"I have a {car.year} {car.make} {car.model}"); 
     } else if (thing is ThingIOwn.Phone phone) {
         Console.WriteLine($"I have a {phone.model} running {phone.OS}");
     }
 }
}