Question

I have an ArrayList of Object (C#).
Each Object has in ID and a Value.

I need to get 1 Random object for Each ID.

Object Class is build in this Way

public class ObjectRandom
{
    int32 id { get; set; }
    string value { get; set;}
}

For Example This ArrayList has 6000 ObjectRandom.

ID’s COULD be sequential or not.

So if there are 500 Objects For Each User that means there are 12 users. (ID1 , ID2 , ID5 , ID10 , ID11, ID15 ID22 ETC).

I would take from The ArrayList (that’s Got ALL 6000 Objects) only 1 ObjectRandom For Each ID’s.

Does it Possible? I’m trying without any result at the moment.

Answer 1

void Main()
{
    var list = new List<ObjectRandom>()
    { 
        new ObjectRandom(){ id = 1, value = "a"},
        new ObjectRandom(){ id = 2, value = "b"},
        new ObjectRandom(){ id = 3, value = "c"},
        new ObjectRandom(){ id = 1, value = "d"},
        new ObjectRandom(){ id = 2, value = "e"},
        new ObjectRandom(){ id = 3, value = "f"},
    };
    var rnd = new Random();
    var q = from a in list.GroupBy (l => l.id)
            let col = a.ToList()
            select col[rnd.Next(0, col.Count)];
}

public class ObjectRandom 
{
    public int id { get; set; }
    public string value { get; set;}
}

If you need to use an ArrayList instead of a generic list use:

from a in list.Cast<ObjectRandom>().GroupBy (l => l.id)