Exercises in .NET with Andras Nemes

Determine if two arrays are structurally equal in C# .NET

Two arrays are said to be structurally equal if they contain the same elements in the same order. Whether or not two elements are the same depends on how you define equality for your custom types. Equality for primitive types, like integers, is more or less straightforward but you’ll need to declare in code what is meant by equality for reference types.

We’ve looked at a couple of strategies to do so on this blog and here we’ll re-use the topic of implementing the IEqualityComparer of T interface.

The non-generic IStructuralEquatable interface has an equals method that accepts an object to compare with and another object which implements the non-generic IEqualityComparer interface. This is an important distinction as implementing the generic IEqualityComparer interface won’t be enough for structural equality. We’ll need to derive from the EqualityComparer base class which implements both the generic and non-generic version of IEqualityComparer. If you try to run the below example with a generic IEqualityComparer of T instance then you’ll get a compiler error.

Note that structural equality is not available for all collection types. Currently only arrays and tuples support it, i.e. they can be cast to type IStructuralEquatable. However, as List objects can be easily converted into arrays that’s not really an obstacle.

Read more of this post

Implementing equality of derived reference types by overriding the == operator with C# .NET

In this post we saw one solution to override the == operator for a reference type to implement equality checking. Here’s a reminder of the Person class:

public class Person
{
	public int Id { get; set; }
	public string Name { get; set; }
	public int Age { get; set; }

	public static bool operator ==(Person personOne, Person personTwo)
	{
		return personOne.Id == personTwo.Id;
	}

	public static bool operator !=(Person personOne, Person personTwo)
	{
		return personOne.Id != personTwo.Id;
	}

        public override int GetHashCode()
	{
		return Id;
	}
}

Read more of this post

Implementing the IEquatable of T interface for object equality in a derived class with C# .NET

In this post we saw how to implement the IEquatable of T interface for a simple Person class. We based our equality logic on the Id property of the object. We implemented the IEquatable.Equals method and also overrode the Object.Equals and GetHashCode methods.

In this post we’ll see how you might go about extending that logic in derived classes. For that purpose we’ll go with another object:

Read more of this post