Implementing C# Linq Distinct on Custom Object List (145 words)

Ever wanted to implement a distinct over a custom object list in C# before? You quickly discover that it fails to work. Sadly there is a lack of decent documentation about this and a lot of FUD. Since I lost a bit of time hopefully this blog post can be picked up as the answer.

Thankfully its not as difficult as you would image. Assuming you have a simple custom object which contains an Id, and you want to use that Id to get a distinct list all you need to do is add the following to the object.

public override bool Equals(object obj)
{
	return this.Id == ((CustomObject)obj).Id;
}

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

You need both due to the way that Linq works. I suspect under the hood its using a hash to work out whats the same hence GetHashCode.