How to Distinct List based on one values from OrderDetails

Question

I have order details:

public class OrderDetails
    {
        public int OrderId { get; set; }
       // [DataMember]
        public int ProductId { get; set; }
    }

Now if I do a distinct like below , it returns everything:

List<OrderDetails> orderDetails = new List<OrderDetails>();
---------------------------------
return orderDetails.Distinct();

But if I do distinct like :

  List<OrderDetails> orderDetails = new List<OrderDetails>();
    ---------------------------------
return orderDetails.Select(x => x.OrderId).Distinct();

Then I get only Order Ids.

How can I get the Distinct Orderdetails(both OrderID and ProductId) based on OrderId

Use `.Where(x => x.OrderId == 4)` – TGlatzer Jan 31 '14 at 11:16 — TGlatzer, Jan 31 '14 at 11:16
`.Select` will return only selected member so use `where` – Jan 31 '14 at 11:17 — , Jan 31 '14 at 11:17

Hamlet Hakobyan · Answer 1 · 2014-01-31T11:36:20.777

1

You can use the overload of Distinct which takes IEqualityComparer<TSource> as comparer.

You can define it as:

public class OrderDetailsEqualityComparer : IEqualityComparer<OrderDetails>
{
    public bool Equals(OrderDetails x, OrderDetails y)
    {
        if (object.ReferenceEquals(x, y))
        {
            return true;
        }

        if (object.ReferenceEquals(x, null) || object.ReferenceEquals(y, null))
        {
            return false;
        }

        return (x.OrderId == y.OrderId );
    }

    public int GetHashCode(Product obj)
    {
        return obj.OrderId.GetHashCode();
    }
}

and use it as:

var osrderedOrderDetails =
       orderDetails.Distinct(new OrderDetailsEqualityComparer());

edited Jan 31 '14 at 11:36

answered Jan 31 '14 at 11:28

Hamlet Hakobyan

32,965
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You can also implement equals and GetHashCode on the class itself – Aron Jan 31 '14 at 11:31
@Aron, I think it is not good idea. In this case you are define the equality relation between the entities at all which can be not necessary. – Hamlet Hakobyan Jan 31 '14 at 11:33

Jignesh Thakker · Answer 2 · 2014-01-31T11:41:12.477

0

Try below code:

Distinct with OrderId

return orderDetails.GroupBy(x => x.OrderId).Select(g => g.First()).ToList();

Distinct with OrderId and ProductId

return orderDetails.GroupBy(x => new {x.OrderId, x.ProductId}).Select(g => g.First()).ToList();

edited Jan 31 '14 at 11:41

answered Jan 31 '14 at 11:21

Jignesh Thakker

3,638
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How is this workin for you??? .Disinct expects a IEquator and you are passing a func !!! – Simsons Jan 31 '14 at 11:23
First GroupBy with property which you want distinct result and after that select first item of group. – Jignesh Thakker Jan 31 '14 at 11:32
Visit http://stackoverflow.com/questions/11811110/c-sharp-select-distinct-by-two-properties-in-a-list SO link. There is a library moreLINQ which has DistinctBy method. – Jignesh Thakker Feb 01 '14 at 17:02

score 0 · Answer 3 · answered Jan 31 '14 at 11:22

You could create a method that takes an Order Id, and return the list as below...

public List<OrderDetails> GetDistinctOrderDetails(int orderId)
{
  List<OrderDetails> orderDetails = GetAllOrders();
  return orderDetails.Where(x => x.OrderId == orderId).Distinct();
}

score 0 · Answer 4 · answered Jan 31 '14 at 11:29

return orderdetails.Where(a=>a.OrderID == _inputvalue).ToArray();

"toarray" can be any of the collection types what ever you need unless your function returns Ienumerable<> then you don't need it

using distinct() is not a good idea as it will drop rows

Samina Azad · Answer 5 · 2014-02-03T04:00:33.267

0

Implement IEquatable interface:

public class OrderDetails : IEquatable<OrderDetails>
{
    public int OrderId { get; set; }

    public int ProductId { get; set; }

    public bool Equals(OrderDetails anotherOrder)
    {
        return this.OrderId.Equals(anotherOrder.OrderId);
    }

    public override int GetHashCode()
    {
        return this.OrderId;
    }
}

Now, try orderDetails.Distinct();

edited Feb 03 '14 at 04:00

answered Jan 31 '14 at 11:36

Samina Azad

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1
4

How to Distinct List based on one values from OrderDetails

5 Answers5