In this code snippet how do I use distinct feature only for e.EntityNumber while selecting all the other values [ e.Firstname, e.Surname, e.EntityNumber ].
response
.Categories
.SelectMany(c => c.Events)
.Select(e => new { e.Firstname, e.Surname, e.EntityNumber })
.Distinct()
.ToList()
You can use GroupBy instead:
response
.Categories
.SelectMany(c => c.Events)
.Select(e => new { e.Firstname, e.Surname, e.EntityNumber })
.GroupBy(x => x.EntityNumber)
.Select(grp => grp.First())
.ToList()
I have selected an arbitrary row of each group (the first). You can change grp.First() according to your logic.
//...
.GroupBy(x => x.EntityNumber)
.Select(grp => grp.OrderBy(x => /* Insert logic here */).First())
//...
You can implement an extension method DistinctBy
public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer = null)
{
if (source == null) throw new ArgumentNullException("source");
if (keySelector == null) throw new ArgumentNullException("keySelector");
var keys = new HashSet<TKey>(comparer);
foreach (var element in source)
{
if (keys.Add(keySelector(element)))
{
yield return element;
}
}
}