Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

C# Intermediate C# Polymorphism Virtual Properties

Nick Martini
Nick Martini
12,846 Points
Posted by Nick Martini
Nick Martini
12,846 Points

What is the purpose of the "=>" operator in this code challenge?

Within the SequenceDetector class, the Description property is being assigned an empty string by using the "=>" operator.

I have never seen this used before in this way. I have always seen properties assigned values by simply using the "=" operator instead.

What are the differences in these two assignments?

RepeatDetector.cs 
namespace Treehouse.CodeChallenges
{
    class RepeatDetector : SequenceDetector
    {
        public override bool Scan(int[] sequence)
        {
            if(sequence.Length < 2)
            {
                return false;
            }

            for(int i = 1; i < sequence.Length; ++i)
            {
                if(sequence[i] == sequence[i-1])
                {
                    return true;
                }
            }

            return false;
        }
    }
}
SequenceDetector.cs 
namespace Treehouse.CodeChallenges
{
    class SequenceDetector
    {
        public string Description => "";

        public virtual bool Scan(int[] sequence)
        {
            return true;
        }
    }
}

1 Answer

Steven Parker
Steven Parker
231,269 Points
Steven Parker
Steven Parker
231,269 Points

That's an "expression-bodied member", not an assignment.

An assignment would create a local field variable, but this creates a property with a custom getter. It's essentially equivalent to this:

public string Description
{
    get { return ""; }
}

This is one of several new features added to C# 6. If you're not still learning C# for the first time, you might want to take a look at What's New in C# 6.