Using GetHashCode() is incorrect. You should cast to int. Using it the way you do is asking for raptors(or Raymond) to come and eat you. That GetHashCode() happens to return the integer value of the enum is an implementation detail and may change in future versions of .net. GetHashCode() guarantees that if two values are … Read more
As others have noted, that is in accordance with the documentation. You must not rely on GetHashCode returning the same thing, ever. The only invariant you can rely upon is that it will return the same value on the same object in the same appdomain if the object has not been mutated in any way … Read more
I came to realize that I wanted Equals to mean two different things, depending on the context. After weighing the input here as well as here, I have settled on the following for my particular situation: I’m not overriding Equals() and GetHashCode(), but rather preserving the common but by no means ubiquitous convention that Equals() … Read more
Table of contents When do I override object.GetHashCode? Why do I have to override object.GetHashCode()? What are those magic numbers seen in GetHashCode implementations? Things that I would like to be covered, but haven’t been yet: How to create the integer (How to “convert” an object into an int wasn’t very obvious to me anyways). … Read more
Be sure to obtain the Reference Source source code when you have questions like this. There’s a lot more to it than what you can see from a decompiler. Pick the one that matches your preferred .NET target, the method has changed a great deal between versions. I’ll just reproduce the .NET 4.5 version of … Read more
How does that work if the fields that it’s based on are mutable? It doesn’t in the sense that the hash code will change as the object changes. That is a problem for all of the reasons listed in the articles you read. Unfortunately this is the type of problem that typically only show up … Read more
Implementing IEquatable<T> for a Value Type Implementing IEquatable<T> for a value type is a little bit different than for a reference type. Let’s assume we have the Implement-Your-Own-Value-Type archetype, a Complex number struct. public struct Complex { public double RealPart { get; set; } public double ImaginaryPart { get; set; } } Our first step … Read more
A bit of background first… Every object in .NET has an Equals method and a GetHashCode method. The Equals method is used to compare one object with another object – to see if the two objects are equivalent. The GetHashCode method generates a 32-bit integer representation of the object. Since there is no limit to … Read more
Domain-Driven Design makes the distinction between Entities and Value Objects. This is a good distinction to observe since it guides how you implement Equals. Entities are equal if their IDs equal each other. Value Objects are equal if all their (important) constituent elements are equal to each other. In any case, the implementation of GetHashCode … Read more
Be sure to obtain the Reference Source source code when you have questions like this. There’s a lot more to it than what you can see from a decompiler. Pick the one that matches your preferred .NET target, the method has changed a great deal between versions. I’ll just reproduce the .NET 4.5 version of … Read more