Correctly using LINQ to shuffle a deck

LINQ methods are not mutating existing collections. So this statement does nothing at all: this.OrderBy(a => Guid.NewGuid()); Also, I'm pretty sure you can't assign to this, so you have to either don't inherit from List<T> (which is good), or do something like this:

var sorted = this.OrderBy(a => Guid.NewGuid()).ToList();
this.Clear();
this.AddRange(sorted);

Also look at this SO answer, there is more correct shuffling algorithm.

Use this extension method

public static class Extensions
{
    public static IEnumerable<T> Randomize<T>(this IEnumerable<T> source)
    {
        Random rnd = new Random();
        return source.OrderBy((item) => rnd.Next());
    }
}

Try this

 public void Shuffle()
 {
     Random r = new Random();
     this.Sort((x, y) => r.Next(-1, 1));
 }

Because of Linq's deffered execution following line doesn't get executed.

this.OrderBy(a => Guid.NewGuid());

This just creates the query but never executed. Even if executed it won't change your collection.

Don't forget Linq is a way to query data, not mutate it.