Question

I have a list of objects that are keyed off or identified uniquely by one of their properties say “ID”. I need to group all the objects of different ID’s that will have rest of properties the same.

Example: Obj has properties “ID”, “E1”, “E2” , “E3”. Note these are all properties of the Obj.

I know ID’s are different for all List of Obj’s, but would like to group if E1,E2 and E3 are same for different Obj’s. So I would have array of Obj’s that have same E1,E2,E3 but different ID’s.

What’s the easiest way of handling this in C#, any ideas?

Answer 1

Well, something like this would work with LINQ:

var groups = collections.GroupBy(x => new { x.E1, x.E2, x.E3 });

That will give you a sequence of groupings you can iterate over. For example:

var groups = collections.GroupBy(x => new { x.E1, x.E2, x.E3 });
foreach (var group in groups)
{
    Console.WriteLine("Key: {0}", group.Key);
    foreach (var item in group)
    {
        Console.WriteLine("  ID: {0}", item.ID);
    }
}