Question

So i have the following generic list:

var topTenSomething = new List<Something>();

Here is Something:

public class Something
{
   public string Name { get; set; }
   public int Rank { get; set; }
}

So i want to randomly assign the “Rank” property, but it needs to be ordered from 1-number of items in the collection.

So if the collection has 3 items, i want to randomly assign ranks from 1 to 3:

1. Some Name
2. Some Other Name
3. Something Else

Then next time, it could be:

1. Some Other Name
2. Some Name
3. Something Else

Know what i mean?

Not sure how to do it – any ideas?

This is for a simple R&D prototype – so don’t worry about performance/why i am doing this. (the real one will have rank assigned by database)

Happy with either a LINQ/non-LINQ version – as long as it works.

Answer 1

Like this:

var rand = new Random();
var sequence = Enumerable.Range(0, list.Count).OrderBy(i => rand.Next()).ToList();

for(var i = 0; i < list.Count; i++)
    list[i].Rank = sequence[i];

If you want the list to be sorted by the random rank:

var rand = new Random();
list.Sort((a, b) => rand.Next(-1, 2));    //Exclusive upper bound
for(var i = 0; i < list.Count; i++)
    list[i].Rank = i;

However, this is not a valid ordering (a < b does not imply b > a) and may cause unexpected results.