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Randomly Sorting a List using Extension Methods

I was trawling through some old code I had written while doing some “refactoring” and came across this little nugget. I wanted to sort a list of objects that I was retrieving from a database using LINQ to SQL into a random order. Seeing as extension methods are all the rage, I decided to use them…

public static class ListExtensions { 
  public static IEnumerable<T> Randomise<T>(this IEnumerable<T> list) { 
    Random rand = new Random();
    var result = list.OrderBy(l => rand.Next());
    return result; 
  } 
}

How does it work…? It adds the Randomise() extension method to the end of any IEnumerable<T> (e.g. List<T>) and uses the OrderBy function to change the sort order based on a randomly generated number.

var randomCategories = context.Categories.Randomise();

The above code will execute the Randomise function to reorder the list of Category objects retrieved from the context randomly and assign the result to randomCategories.