IEqualityComparer for anonymous type

Question

I have this

 var n = ItemList.Select(s => new { s.Vchr, s.Id, s.Ctr, s.Vendor, s.Description, s.Invoice }).ToList();  n.AddRange(OtherList.Select(s => new { s.Vchr, s.Id, s.Ctr, s.Vendor, s.Description, s.Invoice }).ToList();); 

I would like to do this if it where allowed

n = n.Distinct((x, y) => x.Vchr == y.Vchr)).ToList(); 

I tried using the generic LambdaComparer but since im using anonymous types there is no type associate it with.

"Help me Obi Wan Kenobi, you're my only hope"

Answer 1

The trick is to create a comparer that only works on inferred types. For instance:

public class Comparer<T> : IComparer<T> {   private Func<T,T,int> _func;   public Comparer(Func<T,T,int> func) {     _func = func;   }   public int Compare(T x,  T y ) {     return _func(x,y);   } }  public static class Comparer {   public static Comparer<T> Create<T>(Func<T,T,int> func){      return new Comparer<T>(func);   }   public static Comparer<T> CreateComparerForElements<T>(this IEnumerable<T> enumerable, Func<T,T,int> func) {     return new Comparer<T>(func);   } } 

Now I can do the following ... hacky solution:

var comp = n.CreateComparerForElements((x, y) => x.Vchr == y.Vchr);