Custom Equality check for C# 9 records

Custom Equality check for C# 9 records

In C# 9, records provide a convenient way to define classes that are immutable and have value semantics. Records can be compared for equality using the default implementation of the IEquatable<T> interface, which compares all of the properties in the record. However, you can also customize the equality check for a record by implementing the IEquatable<T> interface and overriding the Equals method.

Here's an example of how you can customize the equality check for a record:

public record Person(string FirstName, string LastName, int Age) { public bool Equals(Person other) { if (other is null) { return false; } // Perform your custom equality check here return string.Equals(FirstName, other.FirstName, StringComparison.OrdinalIgnoreCase) && string.Equals(LastName, other.LastName, StringComparison.OrdinalIgnoreCase) && Age == other.Age; } public override bool Equals(object obj) => Equals(obj as Person); public override int GetHashCode() => HashCode.Combine(FirstName, LastName, Age); }

In this example, the Person record implements the IEquatable<T> interface and overrides the Equals method to perform a custom equality check. The custom equality check compares the FirstName, LastName, and Age properties of the record, ignoring case for the FirstName and LastName properties.

The GetHashCode method is also overridden to provide a custom hash code for the record based on its properties.

With this custom implementation of IEquatable<T>, you can compare Person records using the == operator, the != operator, and the Equals method.

Person person1 = new Person("John", "Doe", 30); Person person2 = new Person("JOHN", "DOE", 30); bool areEqual = person1 == person2; // true

Examples

1. "Custom Equality Check using IEquatable for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) : IEquatable<Person> { public bool Equals(Person other) { if (ReferenceEquals(null, other)) return false; if (ReferenceEquals(this, other)) return true; return string.Equals(FirstName, other.FirstName) && string.Equals(LastName, other.LastName); } public override bool Equals(object obj) => Equals(obj as Person); public override int GetHashCode() => HashCode.Combine(FirstName, LastName); }

Description: Implement custom equality checks for a C# 9 record using the IEquatable<T> interface.

2. "Custom Equality Check with ValueTuple for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) { public override bool Equals(object obj) => obj is Person other && (FirstName, LastName).Equals((other.FirstName, other.LastName)); public override int GetHashCode() => (FirstName, LastName).GetHashCode(); }

Description: Implement custom equality checks using ValueTuple for a C# 9 record.

3. "Custom Equality Check with EqualityComparer for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) { public static IEqualityComparer<Person> PersonEqualityComparer { get; } = new PersonEqualityComparer(); private sealed class PersonEqualityComparer : IEqualityComparer<Person> { public bool Equals(Person x, Person y) => x != null && y != null && x.FirstName == y.FirstName && x.LastName == y.LastName; public int GetHashCode(Person obj) => HashCode.Combine(obj.FirstName, obj.LastName); } }

Description: Implement custom equality checks using a dedicated IEqualityComparer<T> for a C# 9 record.

4. "Custom Equality Check with RecordStructuralEqualityComparer for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName); var person1 = new Person("John", "Doe"); var person2 = new Person("John", "Doe"); var areEqual = RecordStructuralEqualityComparer.Default.Equals(person1, person2);

Description: Utilize RecordStructuralEqualityComparer for custom equality checks for C# 9 records.

5. "Custom Equality Check with Equality Operator for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName); public static bool operator ==(Person left, Person right) => Equals(left, right); public static bool operator !=(Person left, Person right) => !Equals(left, right);

Description: Define custom equality operators for C# 9 records.

6. "Custom Equality Check with Value-based Equality for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) { public override bool Equals(object obj) => obj is Person other && (FirstName, LastName).Equals((other.FirstName, other.LastName)); public override int GetHashCode() => (FirstName, LastName).GetHashCode(); }

Description: Implement custom equality checks based on the values of properties for a C# 9 record.

7. "Custom Equality Check with StringComparison for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) { public override bool Equals(object obj) => obj is Person other && FirstName.Equals(other.FirstName, StringComparison.OrdinalIgnoreCase) && LastName.Equals(other.LastName, StringComparison.OrdinalIgnoreCase); public override int GetHashCode() => HashCode.Combine(FirstName.ToUpper(), LastName.ToUpper()); }

Description: Implement custom equality checks with a specific StringComparison for a C# 9 record.

8. "Custom Equality Check with Ignoring Nulls for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) { public override bool Equals(object obj) => obj is Person other && FirstName == other.FirstName && LastName == other.LastName; public override int GetHashCode() => HashCode.Combine(FirstName, LastName); }

Description: Implement custom equality checks ignoring nulls for a C# 9 record.

9. "Custom Equality Check with Property Exclusion for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) { public override bool Equals(object obj) => obj is Person other && FirstName == other.FirstName; public override int GetHashCode() => FirstName.GetHashCode(); }

Description: Implement custom equality checks by excluding specific properties for a C# 9 record.

10. "Custom Equality Check with Case-Insensitive Comparison for C# 9 Records"

Code Implementation:

public record Person(string FirstName, string LastName) { public override bool Equals(object obj) => obj is Person other && FirstName.Equals(other.FirstName, StringComparison.OrdinalIgnoreCase) && LastName.Equals(other.LastName, StringComparison.OrdinalIgnoreCase); public override int GetHashCode() => HashCode.Combine(FirstName.ToUpper(), LastName.ToUpper()); }

Description: Implement custom equality checks with case-insensitive string comparison for a C# 9 record.

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