Skip to content
AtlanticBT Monogram
April 28, 2010

Using .NET 3.5 List.Distinct()

When I was working on a project today, I had a List of objects where I needed to grab objects that had a distinct property value (i.e. where MyObject.MyID is distinct).

I discovered the Distinct() method on the List and I had never used it before so I wasn’t sure of the syntax. After further review, I learned you can use the IEqualityComparer interface to specify how to determine if the object is distinct.

I’ll just show you the code because I feel it’s self explanatory:

public class MyObjectMyIDComparer : IEqualityComparer
{
  public bool Equals(MyObject x, MyObject y)
  {
    return x.MyID == y.MyID;
  }

  public int GetHashCode(MyObject obj)
  {
    return obj.ToString().GetHashCode();
  }
}

Now you can call the Distinct() method and pass in the class:

List MyObjectDistinctMyIDList = MyObjectList.Distinct(new MyObjectMyIDComparer()).ToList();

The Atlantic BT Manifesto

The Ultimate Guide To Planning A Complex Web Project

Partner With Us

Ready for modern web technology and a sharp, user-friendly design? We want to give you exactly that. Contact us to get started.

Contact

Insights

Atlantic BT's Insights

We’re sharing the latest concepts in tech, design, and software development. Learn more about our findings.

Questions & Answers

What is the best web development framework?
Many people commonly ask “what is a framework in web development?” Web development frameworks can easily be confused with web development tools, languages, or parts of the web development stack (like PHP, Ruby, or Javascript).
Learn More
What is the best programming language for web development?
If there was one “best” programming language, then everything else would be obsolete. The reality is that there are so many different programming languages because there is no “best” language for any situation.
Learn More
How much does web development cost?
Web development can vary from a few hundred to millions of dollars depending on what is needed. You may simply need some changes to something that already exists, or you'd like to build a large or complex application.
Learn More
What is PHP web development?
PHP is a back end language primarily used for custom applications, content management systems (such as Wordpress), eCommerce engines (such as Magento), or even massive sites like Facebook.
Learn More
What is the best way to become a web developer?
We get lots of questions from university students working on projects -- How do I get into web development? How long does it take to learn? How much do web developers make?
Learn More
What is front end vs. back end development?
As web development evolved, it separated into logical specialization: front end web development and back end development. While back end development involves the server-side development, front end is the final rendering.
Learn More
What is full stack web development?
Full stack web development as a term evolved due to the separation of roles between front end and back end developers. A “full stack” developer is a developer that can work in both front end and back end technologies.
Learn More