How to Correctly Override Equals() and GetHashCode() for Efficient LINQ Except()?

Correct Implementation of Equals() and GetHashCode() for Custom Class

To effectively utilize the LINQ Except() method for your RecommendationDTO class, you'll need to override the Equals() and GetHashCode() methods.

Equals() Method:

The Equals() method determines if two objects have the same value. Here's an updated implementation:

public override bool Equals(object obj)
{
    var item = obj as RecommendationDTO;

    if (item == null)
    {
        return false;
    }

    return this.RecommendationId.Equals(item.RecommendationId);
}

• It first checks if the passed object can be cast to a RecommendationDTO instance.
• If successful, it compares the RecommendationId properties of both objects.

GetHashCode() Method:

The GetHashCode() method generates a hash code for an object. This is used for faster object comparison and lookup. Here's an updated implementation:

public override int GetHashCode()
{
    return this.RecommendationId.GetHashCode();
}

• It simply returns the hash code of the RecommendationId property.

By overriding Equals() and GetHashCode() like this, you ensure that LINQ's Except() method will accurately identify and exclude duplicate RecommendationDTO objects based on their RecommendationId values.

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