Implementing the IEqualityComparer of T interface for object equality with C# .NET

The generic IEqualityComparer of T provides you a way to indicate whether two custom objects are equal. We’ve looked at equality in a number of posts on this blog – see the link below if you’re curious – and IEqualityComparer fulfils a similar purpose though its usage is different.

Equality comparers are most often used to filter out duplicates from a collection.

Consider the following class:

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Implementing the IEquatable of T interface for object equality with C# .NET

In this short post we’ll see a way how to make two custom objects equatable using the generic IEquatable interface. Consider the following object:

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

The object superclass has an Equals method that we can test as follows:

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Structurally compare two arrays in .NET

In this post we saw how to determine if two arrays are structurally equal in .NET. Two arrays are said to be structurally equal if they contain the same elements in the same order.

Structural equality has a comparison counterpart: IStructuralComparable. It determines if an array comes before or after or is equal to another array based on the elements within it.

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Using the StringComparer class for string equality with C# .NET

In this post we saw how to use the generic IEqualityComparer of T interface to indicate equality for our custom types. If you need a similar comparer for strings then there’s a ready-made static class called StringComparer which can construct string comparers for you.

The StringComparer class provides comparers for the common string comparison scenarios: ordinal, locale specific and invariant culture comparisons. This is a good MSDN article on the differences between these.

Read more of this post

Structurally compare two arrays in .NET

In this post we saw how to determine if two arrays are structurally equal in .NET. Two arrays are said to be structurally equal if they contain the same elements in the same order.

Structural equality has a comparison counterpart: IStructuralComparable. It determines if an array comes before or after or is equal to another array based on the elements within it.

Read more of this post

Using the StringComparer class for string equality with C# .NET

In this post we saw how to use the generic IEqualityComparer of T interface to indicate equality for our custom types. If you need a similar comparer for strings then there’s a ready-made static class called StringComparer which can construct string comparers for you.

The StringComparer class provides comparers for the common string comparison scenarios: ordinal, locale specific and invariant culture comparisons. This is a good MSDN article on the differences between these.

Read more of this post

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

In this post we saw how to implement the generic IEquatable interface to make two custom objects equatable using the static Equals method.

You’re probably aware of the equality operator ‘==’ in C#. Let’s see what happens if you try to use it for a custom object:

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

Read more of this post

Structurally compare two arrays in .NET

In this post we saw how to determine if two arrays are structurally equal in .NET. Two arrays are said to be structurally equal if they contain the same elements in the same order.

Structural equality has a comparison counterpart: IStructuralComparable. It determines if an array comes before or after or is equal to another array based on the elements within it.

Read more of this post