CODEWITHSUNDEEP
c#
Leonardo Bonetti
Leonardo Bonetti

Reputation: 177

Randomize a List of objects about a seed number

I have the object:

public class Object{
    public String ID{get;set;}
}

And my software receive a List:

List<Object> objs = new List<Object>();
objs.add(new Object{ID = "1"});
objs.add(new Object{ID = "2"});
objs.add(new Object{ID = "3"});
objs.add(new Object{ID = "4"});

And then I randomize it:

objs = objs.OrderBy(a => Guid.NewGuid()).ToList();
Debug.WriteLine(objs.ID);
// 1 4 2 3

If I execute objs.OrderBy(a => Guid.NewGuid()).ToList(); i'm going to receive another random sequence // 3 2 4 1.

I need to pass a "seed"(a integer number) and randomize about this number, for example, if I pass the seed 1 I receive // 3 2 4 1, when I execute the number 1 again i need to receive the same order // 3 2 4 1.

There is a way to do it in c#?

Edit: The object above is just a example, the real case i need to randomize the following object:

public class Object{
    public Int ID{get;set;}
    public String ImageTitle{get;set;}
    public String ImageDescription{get;set;}
    public String Url {get;set;}
}

Upvotes: 0

Views: 203

Answers (2)

wikiCan
wikiCan

Reputation: 449

Use this method and cache randomized arrays and serve it again. easy.

    private Dictionary<int, List<Object>> randoms=new Dictionary<int, List<Object>>();

    private List<Object> GetRandom(List<Object> objs,int? seed)
    {
        if (seed == null)
        {
            return objs.OrderBy(a => Guid.NewGuid()).ToList();
        }
        else
        {
            if (!randoms.ContainsKey(seed.Value))
            randoms[seed.Value] = objs.OrderBy(a => Guid.NewGuid()).ToList();

            return randoms[seed.Value];
        }
    }

Example call GetRandom(objs,null) will always randomize it. If you call it with number GetRandom(objs,1) he will serve old randomized array.

Upvotes: 0

Zohar Peled
Zohar Peled

Reputation: 82474

Not with GUID, but with Random it's not only possible but easy:

var seed = 123;
var r = new Random(seed);
objs = objs.OrderBy(o => r.Next()).ToList();

You can see a live demo on rextester.

Upvotes: 3

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