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
IEqualityComparer<T> is an interface for an object that performs the comparison on two objects of the type T. IEquatable<T> is for an object of type T so that it can compare itself to another of the same type.
The main reason is performance. When generics were introduced in .NET 2.0 they were able to add a bunch of neat classes such as List<T>, Dictionary<K,V>, HashSet<T>, etc. These structures make heavy use of GetHashCode and Equals. But for value types this required boxing. IEquatable<T> lets a structure implement a strongly typed Equals method so … Read more
LINQ Distinct is not that smart when it comes to custom objects. All it does is look at your list and see that it has two different objects (it doesn’t care that they have the same values for the member fields). One workaround is to implement the IEquatable interface as shown here. If you modify … Read more