I'm using unity, and unity does not have a tuple in it, so I created my own tuple class to work since I needed it for my Dictionary.
Dictionary <Tuple<int,int>, Tile>
Tile class that I created and isn't really relevant to solve this problem(at least I think it wont help).
But the problem is that I'm using both negative and positive integer in my tuples, and when I use my current GetHashCode() with the Tuples, sometimes I get the same HashCode, for example Tuple<-10, 8> and Tuple<-9,-10> both gives -172 when I return the hashcode.
Is there any good GetHashCode that wouldn't get me conflicts?
To be honest I'm only using the operator ==, because I need to check if both tuples have the same integers inside of them, if I could get a operator == that only collides when both integer are the same and in the same order, it would solve my problem.
Some other minor problems, I can't get to understand the Equals override, as it is, it is working, but I don't know how well it works, since I kind of changed every single thing until it worked.
public class Tuple<T1, T2>
{
public T1 First { get; private set; }
public T2 Second { get; private set; }
public Tuple(T1 _First, T2 _Second)
{
First = _First;
Second = _Second;
}
public override int GetHashCode()
{
int hash = 0;
hash = First.GetHashCode() * 17 + Second.GetHashCode() + First.GetHashCode();
return hash;
}
public static bool operator==(Tuple<T1, T2> obj1, Tuple<T1, T2> obj2)
{
if (ReferenceEquals(null, obj2))
return false;
return (obj1.GetHashCode() == obj2.GetHashCode());
}
public static bool operator!=(Tuple<T1, T2> obj1, Tuple<T1, T2> obj2)
{
if (ReferenceEquals(null, obj2))
return true;
return !(obj1.GetHashCode() == obj2.GetHashCode());
}
public bool Equals(Tuple<T1, T2> other)
{
if (other == null)
return false;
if (GetHashCode() == other.GetHashCode())
return true;
else
return false;
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj))
{
return false;
}
if (ReferenceEquals(this, obj))
{
return true;
}
Tuple<T1, T2> other = obj as Tuple<T1, T2>;
return obj.GetType() == GetType() && Equals(other);
}
}
public static class Tuple
{
public static Tuple<T1, T2> New<T1, T2>(T1 first, T2 second)
{
var tuple = new Tuple<T1, T2>(first, second);
return tuple;
}
}
GetHashCode() isn't supposed to be collision free. You should use it to determine if two things might be the same objects, and then you have to actually do a thorough check to see if they are.
For example, your == method should be written more like this:
public static bool operator==(Tuple<T1, T2> obj1, Tuple<T1, T2> obj2)
{
if (ReferenceEquals(null, obj2))
return false;
if (obj1.GetHashCode() != obj2.GetHashCode())
{
return false;
}
return DefaultComparer<T1>.Equals(obj1.First, obj2.First) && DefaultComparer<T2>.Equals(obj1.Second, obj2.Second);
}
Also, don't forget to consider the case where obj1 and obj2 are both null.
If you're implementing your own Tuple, you might consider just stealing Microsoft's from the Reference Source repository, or at least use it as a base for your own.
I'm using unity, and unity does not have a tuple in it
It supports Tuple if you have Unity 2017 and above.
Go to Edit --> Project Settings --> Player --> Other Settings --> Configuration --> Scripting Runtime Version --> .NET 4.x Equivalent.
Reload or restart Visual Studio and you should be able to use Tuple. If you are not using Unity 2017 and above and also don't want to update then see John's answer.
This is what resharper generates for you automatically. Just note how they do the GetHashCode() and Equals.
private class Tuple<T1,T2> : IEquatable<Tuple<T1, T2>>
{
public T1 First {get;}
public T2 Second {get;}
public Tuple(T1 first, T2 second)
{
First = first;
Second = second;
}
public bool Equals(Tuple<T1, T2> other)
{
if (ReferenceEquals(null, other)) return false;
if (ReferenceEquals(this, other)) return true;
return EqualityComparer<T1>.Default.Equals(First, other.First) && EqualityComparer<T2>.Default.Equals(Second, other.Second);
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj)) return false;
if (ReferenceEquals(this, obj)) return true;
if (obj.GetType() != this.GetType()) return false;
return Equals((Tuple<T1, T2>) obj);
}
public override int GetHashCode()
{
unchecked
{
return (EqualityComparer<T1>.Default.GetHashCode(First) * 397) ^ EqualityComparer<T2>.Default.GetHashCode(Second);
}
}
public static bool operator ==(Tuple<T1, T2> left, Tuple<T1, T2> right)
{
return Equals(left, right);
}
public static bool operator !=(Tuple<T1, T2> left, Tuple<T1, T2> right)
{
return !Equals(left, right);
}
}
I have found PropertyCompare (*) to be useful in auto-generating Equals implementations. It will automatically compare all public properties (so if you add a new public property you don't need to change anything except GetHashCode (and even that is technically optional).
It uses Cache to be reasonably performant - it takes a one-off hit (per type) to generate the appropriate expressions for the comparisons.
using System;
using System.Linq.Expressions;
namespace YourApp
{
public class Tuple<T1, T2>
{
public T1 First { get; private set; }
public T2 Second { get; private set; }
public Tuple(T1 _First, T2 _Second)
{
First = _First;
Second = _Second;
}
public override int GetHashCode()
{
var hash = 0;
// Implement this however you like
hash = First.GetHashCode() * 17 + Second.GetHashCode() + First.GetHashCode();
return hash;
}
public static bool operator ==(Tuple<T1, T2> x, Tuple<T1, T2> y)
{
return PropertyCompare.Equal(x, y);
}
public static bool operator !=(Tuple<T1, T2> x, Tuple<T1, T2> y)
{
return !PropertyCompare.Equal(x, y);
}
public bool Equals(Tuple<T1, T2> other)
{
return PropertyCompare.Equal(this, other);
}
public override bool Equals(object obj)
{
return PropertyCompare.Equal(this, obj);
}
}
public static class Tuple
{
public static Tuple<T1, T2> New<T1, T2>(T1 first, T2 second)
{
var tuple = new Tuple<T1, T2>(first, second);
return tuple;
}
}
public class Program
{
public static void Main()
{
var bob1 = Tuple.New("a", 1);
var bob2 = Tuple.New("a", 1);
Console.WriteLine(bob1 == bob2);
Console.ReadLine();
}
}
public static class PropertyCompare
{
public static bool Equal<T>(T x, object y) where T : class
{
return Cache<T>.Compare(x, y as T);
}
public static bool Equal<T>(T x, T y)
{
if (x == null)
{
return y == null;
}
if (y == null)
{
return false;
}
return Cache<T>.Compare(x, y);
}
private static class Cache<T>
{
internal static readonly Func<T, T, bool> Compare;
static Cache()
{
var props = typeof(T).GetProperties();
if (props.Length == 0)
{
Compare = delegate { return true; };
return;
}
var x = Expression.Parameter(typeof(T), "x");
var y = Expression.Parameter(typeof(T), "y");
Expression body = null;
for (var i = 0; i < props.Length; i++)
{
var propEqual = Expression.Equal(
Expression.Property(x, props[i]),
Expression.Property(y, props[i]));
if (body == null)
{
body = propEqual;
}
else
{
body = Expression.AndAlso(body, propEqual);
}
}
Compare = Expression.Lambda<Func<T, T, bool>>(body, x, y)
.Compile();
}
}
}
}
(*) I found it online somewhere, alas I can't remember where and Google is failing me here.
Related
I'm trying to create a Dictionary is C# that takes an Unordered Pair of Indices as its Key.
For example:
exampleDictionary[new UnorderedPair(x,y)] and exampleDictionary[new UnorderedPair(y,x)] should both return the same value.
Is there a way to create a custom unordered collection other than using a HashSet? Or some way to create an unordered Tuple?
This question is similar to what I'm trying to accomplish, except in C# rather than python.
If the type is not your own or you can't or don't want to modify refer to Theodor Zoulias's answer
Otherwise, assuming that UnorderedPair is your own class you can modify what you could do is e.g.
[Serializable]
public class UnorderedPair<T> : IEquatable<UnorderedPair<T>>
{
public T X;
public T Y;
public UnorderedPair()
{
}
public UnorderedPair(T x, T y)
{
X = x;
Y = y;
}
public bool Equals(UnorderedPair<T> other)
{
if (ReferenceEquals(null, other))
{
return false;
}
if (ReferenceEquals(this, other))
{
return true;
}
// For equality simply include the swapped check
return X.Equals(other.X) && Y.Equals(other.Y) || X.Equals(other.Y) && Y.Equals(other.X);
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj))
{
return false;
}
if (ReferenceEquals(this, obj))
{
return true;
}
if (obj.GetType() != GetType())
{
return false;
}
return Equals((UnorderedPair<T>)obj);
}
public override int GetHashCode()
{
// and for the HashCode (used as key in HashSet and Dictionary) simply order them by size an hash them again ^^
var hashX = X == null ? 0 : X.GetHashCode();
var hashY = Y == null ? 0 : Y.GetHashCode();
return HashCode.Combine(Math.Min(hashX,hashY), Math.Max(hashX,hashY));
}
public static bool operator ==(UnorderedPair<T> left, UnorderedPair<T> right)
{
return Equals(left, right);
}
public static bool operator !=(UnorderedPair<T> left, UnorderedPair<T> right)
{
return !Equals(left, right);
}
}
and then e.g.
var testDict = new Dictionary<UnorderedPair<int>, string>();
testDict.Add(new UnorderedPair<int>(1,2), "Hello World!");
Console.WriteLine(testDict[new UnorderedPair<int>(2,1)]);
As per suggestion by Jodrell in the comments you could even make the types swappable - not sure this would be ever needed - but this way you could even have a pair of different types:
[Serializable]
public class UnorderedPair<TX, TY> : IEquatable<UnorderedPair<TX, TY>>
{
public TX X;
public TY Y;
public UnorderedPair()
{
}
public UnorderedPair(TX x, TY y)
{
X = x;
Y = y;
}
public UnorderedPair(TY y, TX x)
{
X = x;
Y = y;
}
public override int GetHashCode()
{
// and for the HashCode (used as key in HashSet and Dictionary) simply order them by size an hash them again ^^
var hashX = X == null ? 0 : X.GetHashCode();
var hashY = Y == null ? 0 : Y.GetHashCode();
var combine = HashCode.Combine(Math.Min(hashX, hashY), Math.Max(hashX, hashY));
return combine;
}
public bool Equals(UnorderedPair<TX, TY> other)
{
if (ReferenceEquals(null, other))
{
return false;
}
if (ReferenceEquals(this, other))
{
return true;
}
if (typeof(TX) != typeof(TY))
{
return EqualityComparer<TX>.Default.Equals(X, other.X) && EqualityComparer<TY>.Default.Equals(Y, other.Y);
}
return EqualityComparer<TX>.Default.Equals(X, other.X) && EqualityComparer<TY>.Default.Equals(Y, other.Y)
|| X.Equals(other.Y) && Y.Equals(other.X);
}
public override bool Equals(object obj)
{
if (ReferenceEquals(null, obj))
{
return false;
}
if (ReferenceEquals(this, obj))
{
return true;
}
return obj switch
{
UnorderedPair<TX, TY> other => Equals(other),
UnorderedPair<TY, TX> otherSwapped => Equals(otherSwapped),
_ => false
};
}
public static bool operator ==(UnorderedPair<TX, TY> left, UnorderedPair<TX, TY> right)
{
return Equals(left, right);
}
public static bool operator !=(UnorderedPair<TX, TY> left, UnorderedPair<TX, TY> right)
{
return !Equals(left, right);
}
public static implicit operator UnorderedPair<TX, TY>(UnorderedPair<TY, TX> pair)
{
return new UnorderedPair<TX, TY>(pair.Y, pair.X);
}
}
and
var testDict = new Dictionary<UnorderedPair<int, double>, string>();
testDict.Add(new UnorderedPair<int, double>(1,2.5), "Hello World!");
Console.WriteLine(testDict[new UnorderedPair<double,int>(2.5,1)]);
(.NET Fiddle for both)
You could write a custom IEqualityComparer<UnorderedPair<T>> implementation, and pass it as argument to the constructor of your Dictionary<UnorderedPair<TKey>, TValue>. This way you won't have to modify your UnorderedPair<T> type, by overriding its Equals and GetHashCode methods. Below is an example of such a comparer for the ValueTuple<T1, T2> struct, with both T1 and T2 being the same type:
class UnorderedValueTupleEqualityComparer<T> : IEqualityComparer<(T, T)>
{
private readonly IEqualityComparer<T> _comparer;
public UnorderedValueTupleEqualityComparer(IEqualityComparer<T> comparer = default)
{
_comparer = comparer ?? EqualityComparer<T>.Default;
}
public bool Equals((T, T) x, (T, T) y)
{
if (_comparer.Equals(x.Item1, y.Item1)
&& _comparer.Equals(x.Item2, y.Item2)) return true;
if (_comparer.Equals(x.Item1, y.Item2)
&& _comparer.Equals(x.Item2, y.Item1)) return true;
return false;
}
public int GetHashCode((T, T) obj)
{
int h1 = _comparer.GetHashCode(obj.Item1);
int h2 = _comparer.GetHashCode(obj.Item2);
if (h1 > h2) (h1, h2) = (h2, h1);
return HashCode.Combine(h1, h2);
}
}
Usage example:
Dictionary<(int, int), string> dictionary = new(
new UnorderedValueTupleEqualityComparer<int>());
Inspired by #derHugo's answer and my comments on it,
Fiddle here
A generic implementation,
#nullable enable
public class UnorderedPair<T> : IEquatable<UnorderedPair<T>>
{
private static IEqualityComparer<T> comparer = EqualityComparer<T>.Default;
public T X { get; }
public T Y { get; }
public UnorderedPair(T x, T y)
{
X = x;
Y = y;
}
public bool Equals(UnorderedPair<T>? other)
{
if(other is null)
{
return false;
}
if (ReferenceEquals(this, other))
{
return true;
}
// For equality simply include the swapped check
return
comparer.Equals(X, other.X) && comparer.Equals(Y, other.Y)
||
comparer.Equals(X, other.Y) && comparer.Equals(Y, other.X);
}
public override bool Equals(object? obj)
{
return Equals(obj as UnorderedPair<T>);
}
public override int GetHashCode()
{
unchecked
{
return
(X is null ? 0 : comparer.GetHashCode(X))
+
(Y is null ? 0 : comparer.GetHashCode(Y));
}
}
public static bool operator ==(UnorderedPair<T>? left, UnorderedPair<T>? right)
{
return Equals(left, right);
}
public static bool operator !=(UnorderedPair<T>? left, UnorderedPair<T>? right)
{
return !Equals(left, right);
}
}
#nullable disable
I have a Stateful Service Fabric service and create, update or read data using IReliableDictionary created with the following code:
var dictionary = await StateManager.GetOrAddAsync<IReliableDictionary<string, Entry>>(ReliableDictionaryName);
// Read
using (ITransaction tx = StateManager.CreateTransaction())
{
ConditionalValue<Entry> result = await dictionary.TryGetValueAsync(tx, name);
return result.HasValue ? result.Value : null;
}
// Create or update
using (ITransaction tx = StateManager.CreateTransaction())
{
await dictionary.AddOrUpdateAsync(tx, entry.Name, entry, (key, prev) => entry);
await tx.CommitAsync();
}
It works, but it is case-sensitive.
Is there any way to make Reliable collection store and get data in a case-insensitive way, except for applying .ToLower() to the keys, which is kind of hacky?
This behavior you see is mostly a property of how strings are compared by default in C#. Reliable dictionaries use a key's implementation of IEquatable and IComparable to perform lookups. If the default behavior of string doesn't work for you, you can implement a type that performs string comparisons the way you want. Then, use the new type as the key for your reliable dictionary. You could implement implicit operators to convert between raw strings and the custom type to make usage painless. Here's an example:
using System.Runtime.Serialization;
[DataContract]
public class CaseInsensitiveString : IEquatable<CaseInsensitiveString>,
IComparable<CaseInsensitiveString>
{
#region Constructors
public CaseInsensitiveString(string value)
{
this.Value = value;
}
#endregion
#region Instance Properties
[DataMember]
public string Value
{
get;
set;
}
#endregion
#region Instance Methods
public override bool Equals(object obj)
{
if (ReferenceEquals(null,
obj))
{
return false;
}
if (ReferenceEquals(this,
obj))
{
return true;
}
if (obj.GetType() != this.GetType())
{
return false;
}
return this.Equals((CaseInsensitiveString)obj);
}
public override int GetHashCode()
{
return this.Value != null
? this.Value.GetHashCode()
: 0;
}
public int CompareTo(CaseInsensitiveString other)
{
return string.Compare(this.Value,
other?.Value,
StringComparison.OrdinalIgnoreCase);
}
public bool Equals(CaseInsensitiveString other)
{
if (ReferenceEquals(null,
other))
{
return false;
}
if (ReferenceEquals(this,
other))
{
return true;
}
return string.Equals(this.Value,
other.Value,
StringComparison.OrdinalIgnoreCase);
}
#endregion
#region Class Methods
public static bool operator ==(CaseInsensitiveString left,
CaseInsensitiveString right)
{
return Equals(left,
right);
}
public static implicit operator CaseInsensitiveString(string value)
{
return new CaseInsensitiveString(value);
}
public static implicit operator string(CaseInsensitiveString caseInsensitiveString)
{
return caseInsensitiveString.Value;
}
public static bool operator !=(CaseInsensitiveString left,
CaseInsensitiveString right)
{
return !Equals(left,
right);
}
#endregion
}
So I am creating a BST and want it to be a generic tree, right now I am developing the Node<T> class. I need some help with some of the operator overloading specifics. Class is below:
public class Node<T> where T : IComparable
{
//Private member data
private T data;
private Node<T> left;
private Node<T> right;
//private readonly IComparer<T> _comparer;
//Node constructor
public Node()
{
data = default(T); //
left = null;
right = null;
}
//Setters/getters for node private data members
public T Data
{
get { return data; }
set { data = value; }
}
public Node<T> Left
{
get { return left; }
set { left = value; }
}
public Node<T> Right
{
get { return right; }
set { right = value; }
}
public static bool operator ==(Node<T> lhs, Node<T> rhs)
{
if((lhs.Data).CompareTo(rhs.Data) == 0)
{
return true;
}
else
{
return false;
}
}
public static bool operator !=(Node<T> lhs, Node<T> rhs)
{
if (lhs.Data.CompareTo(rhs.Data) != 0)
{
return true;
}
else
{
return false;
}
}
}
But Visual Studio (and sources I have seen online) say I need to overload the Object.Equals(object o) method and also the Object.GetHashCode.
From what I know about .Equals just through using C#, it's like value type semantics, or will compare the values of 2 objects, instead of their references, aka checking if they are actually the same object, which I think is what == usually does when comparing objects. So this is what I tried to do:
public override bool Equals(Object obj)
{
if ((lhs.Data).CompareTo(rhs.Data) == 0)
{
return true;
}
else
{
return false;
}
}
It's basically the same as my == operator, but it doesn't work because the lhs/rhs parameters don't exist. I have no idea how do accomplish this for my case since how I believe it will be called is n1.Equals(n2) and will check to see if the data values are the same for the nodes. Examples online are unclear to me. I also have no idea why I have to involve this hash method at all, but I am still trying to do research on that. Mostly curious about the Equals override for now.
Make sure you implement the Equals method according to the MS guide. Here is my snippet. I use all the time:
// override object.Equals
public override bool Equals(object obj)
{
// shortcut
if (object.ReferenceEquals(this, obj))
{
return true;
}
// check for null and make sure we do not break oop / inheritance
if (obj == null || GetType() != obj.GetType())
{
return false;
}
// TODO: write your implementation of Equals() here
// do not call base.equals !
throw new NotImplementedException();
return false;
}
public static bool operator ==(Class lobj, Class robj)
{
// users expect == working the same way as Equals
return object.Equals(lobj, robj);
}
public static bool operator !=(Class lobj, Class robj)
{
return !object.Equals(lobj, robj);
}
// override object.GetHashCode
public override int GetHashCode()
{
// TODO: write your implementation of GetHashCode() here
// return field.GetHashCode() ^ field2.GetHashCode() ^ base.GetHashCode();
// or simply return the unique id if any
throw new NotImplementedException();
}
Anyone can explain these codes for me?
public class SimilarityImages : IComparer<SimilarityImages>, IComparable
{
private readonly ComparableImage source;
private readonly ComparableImage destination;
private readonly double similarity;
public SimilarityImages(ComparableImage source, ComparableImage destination, double similarity)
{
this.source = source;
this.destination = destination;
this.similarity = similarity;
}
public ComparableImage Source
{
get
{
return source;
}
}
public ComparableImage Destination
{
get
{
return destination;
}
}
public double Similarity
{
get
{
return Math.Round(similarity * 100, 1);
}
}
public static int operator !=(SimilarityImages value, SimilarityImages compare)
{
return value.CompareTo(compare);
}
public static int operator <(SimilarityImages value, SimilarityImages compare)
{
return value.CompareTo(compare);
}
public static int operator ==(SimilarityImages value, SimilarityImages compare)
{
return value.CompareTo(compare);
}
public static int operator >(SimilarityImages value, SimilarityImages compare)
{
return value.CompareTo(compare);
}
public override string ToString()
{
return string.Format("{0}, {1} --> {2}", source.File.Name, destination.File.Name, similarity);
}
#region IComparer<SimilarityImages> Members
public int Compare(SimilarityImages x, SimilarityImages y)
{
return x.similarity.CompareTo(y.similarity);
}
#endregion
#region IComparable Members
public int CompareTo(object obj)
{
SimilarityImages other = (SimilarityImages)obj;
return this.Compare(this, other);
}
#endregion
public override bool Equals(object obj)
{
if (obj == null || GetType() != obj.GetType())
{
return false;
}
var other = (SimilarityImages)obj;
var equals = Source.File.FullName.Equals(other.Source.File.FullName, StringComparison.InvariantCultureIgnoreCase);
if (!equals)
{
return false;
}
equals = Destination.File.FullName.Equals(other.Destination.File.FullName, StringComparison.InvariantCultureIgnoreCase);
if (!equals)
{
return false;
}
return true;
}
public override int GetHashCode()
{
return string.Format("{0};{1}", Source.File.FullName, Destination.File.FullName).GetHashCode();
}
}
It looks kind of like String.Compare()
(Comparison of strings by value.)
however the return of integers for the operators <, >, <=, >=, ==, != is a bad practice - user expect a boolean return value.
Also, if the "images" are what I think they are (images as in a matrix of pixels), then returning a value for comparison is not intuitive - What comparison algorithm are you using? - Why are you providing only one comparison algorithm and hiding its name? - What if the images are not of same size or pixel format?
I have a custom object that maps a boolean value from a legacy database to a C# bool (and back again).
My custom bool object looks like this:
public class S2kBool : IUserDefinedType {
public bool Value { get; set; }
public Type SupportedType { get { return typeof(string); } }
// These are the values used to represent booleans in the database
public const string TrueValue = "Y";
public const string FalseValue = "N";
public static S2kBool True {
get { return new S2kBool(true); }
}
public static S2kBool False {
get { return new S2kBool(false); }
}
public S2kBool() : this(false) { }
public S2kBool(bool value) {
this.Value = value;
}
// Called when a property of this type is populated from the database
public void FromSimpleDataType(object value) {
this.Value = value.ToString() == TrueValue;
}
// Called when a property of this type is inserted into the database
public object ToSimpleDataType() {
return this.Value ? TrueValue : FalseValue;
}
}
I would like to be able to do something like this:
public class TestObject {
public S2kBool IsActive = S2kBool.True;
}
TestObject tObj = new TestObject();
if (tObj.IsActive == S2kBool.True) {
// the above would evaluate to true
}
I've seen a few different methods for doing comparisons between objects, but I'm not sure of which one to use.
EDIT: Better yet, would it be possible to do something like the following and have C# treat the S2kBool object as an actual Boolean during comparison? It should also allow comparisons with other S2kBool objects, as well.
if (tObj.IsActive == true) { ... }
There are 2 things to look at; an implicit conversion operator (in S2kBool) to bool, or the true/false operators themselves...
true/false operators (note I prefer the implicit bool conversion myself):
public static bool operator true(S2kBool x) {
return x.Value;
}
public static bool operator false(S2kBool x) {
return !x.Value;
}
then you can use if(tObj.IsActive)
conversion operator:
public static implicit operator bool(S2kBool x) {
return x.Value;
}
works likewise
You might also add a conversion in the other direction:
public static implicit operator S2kBool(bool x)
{
return new S2kBool(x);
}
Then you can assign IsActive = false; etc
Finally, I wonder if this should be an immutable struct? It might be confusing if you expect this to behave like a value. For example, look at the last line here:
TestObject obj1 = new TestObject(),
obj2 = new TestObject();
obj1.IsActive = obj2.IsActive = S2kBool.True;
Console.WriteLine(obj1.IsActive);
Console.WriteLine(obj2.IsActive);
obj1.IsActive.Value = false;
Console.WriteLine(obj1.IsActive);
Console.WriteLine(obj2.IsActive); // what does this print?
This prints false, because both IsActive fields point to the same instance of S2kBool. If that was the intent, then fine. But if it was me, I'd make it immutable (whether class or struct). But since it doesn't really have any state other than a bool, I'd argue that this fits well as a struct.
To be honest, I'm not entirely sure why it is needed at all, when all the functionality could be done via static methods / etc.
Yes, you can do that. You would need to define equality operators and override the Equals method.
Here is an article about operator overloading:
http://www.csharphelp.com/archives/archive135.html
Here is an example of a type with overridden equality operators. You can do the same with assignment and conversion operators, making your type work seamlessly with the built-in bool type. (I took your example, shortened it a bit to keep the example short, and added the equality operators).
public struct S2kBool : IEquatable<bool>
{
public bool Value { get; set; }
public bool Equals(bool other)
{
return Value == other;
}
public override int GetHashCode()
{
return Value.GetHashCode();
}
public static bool operator ==(bool left, S2kBool right)
{
return right.Equals(left);
}
public static bool operator !=(bool left, S2kBool right)
{
return !(left == right);
}
public static bool operator ==(S2kBool left, bool right)
{
return left.Equals(right);
}
public static bool operator !=(S2kBool left, bool right)
{
return !(left == right);
}
}